ISA Certified Arborist Exam Guide
Short answer: the ISA Certified Arborist exam has 200 multiple-choice questions (180 scored, 20 unscored), you have 3.5 hours, and the passing score is 76%. To apply you need three years of full-time arboriculture experience, or a mix of education and experience. Exam enrollment costs $295 for ISA members or $369 for non-members, plus a $40 or $50 application fee. Certification lasts three years.
Source: ISA Certified Arborist Program Guide (revised August 2025), checked October 19, 2026. ISA can change fees and rules; confirm on isa-arbor.com before you apply.
Certified arborist exam format
- 200 multiple-choice questions, each with four choices and one correct answer.
- 210 minutes (3.5 hours). Restroom breaks count against your time.
- 20 of the questions are new trial questions that do not count toward your score. They are not marked, so treat every question as if it counts.
- Computer-based at Pearson VUE test centers, or on paper at events run by local ISA Certification Partners.
- No books, notes, phones or food in the testing room.
At about a minute per question, pacing matters. If a question stalls you, mark your best guess and move on; there is no stated penalty for a wrong answer, so never leave one blank.
What the arborist certification exam covers
The exam is built from ISA's job task analysis (Job Task Analysis 2022) and split into ten domains. The percentage is the share of questions from each domain.
| Domain | Share of exam | ≈ Questions | Free practice |
|---|---|---|---|
| Tree Biology | 11% | 22 | 10 questions |
| Tree Identification and Selection | 9% | 18 | 10 questions |
| Soil Management | 7% | 14 | 10 questions |
| Installation and Establishment | 9% | 18 | 10 questions |
| Pruning | 14% | 28 | 10 questions |
| Diagnosis and Treatment | 9% | 18 | 10 questions |
| Trees and Construction | 9% | 18 | 10 questions |
| Tree Risk | 11% | 22 | 10 questions |
| Safe Work Practices | 15% | 30 | 10 questions |
| Urban Forestry | 6% | 12 | 10 questions |
Weights from the ISA Certified Arborist Program Guide (exam outline based on the Job Task Analysis 2022). "≈ Questions" is the weight applied to 200 questions; ISA does not publish exact per-domain counts.
Safe Work Practices (15%) and Pruning (14%) together make up more than a quarter of the exam. Urban Forestry (6%) and Soil Management (7%) are the smallest, but skipping them is a gamble you don't need to take.
Sample certified arborist exam questions
The real exam asks 200 multiple-choice questions like these, each with four choices and one correct answer. Here is one from each of the 5 heaviest domains. Pick an answer to see the explanation and its source.
A climber is ready to cut a limb that will free-fall into the drop zone below. Which communication step should come before the cut?
Show answer and explanation
Correct answer: C. The climber calls “stand clear” and waits for an “all clear” reply from below
Tree crews use a command-and-response system: the worker aloft gives a clear command and does not cut until someone below answers that the drop zone is clear. OSHA's tree care guidance gives “stand clear” from the climber and “all clear” from the ground as its example. A worker being out of sight, the sound of a saw starting, or a shout after the limb is already falling does not confirm that everyone is out of the drop zone.
- A: Being out of the climber's sight does not confirm the worker is clear of the drop zone; the climber needs a spoken reply.
- B: A saw starting is not a command and gives no confirmed warning of when the limb will drop.
- D: A warning given after the cut leaves no time to clear the drop zone; the exchange must be completed before cutting.
Source: Solutions for Tree Care Hazards (OSHA 3940), Occupational Safety and Health Administration (OSHA)
Report a problem with this question · ID safe-002
A mature street tree has a broken limb hanging over a sidewalk, two rubbing branches in its interior, and a lopsided crown. Following the priority order in the USDA Forest Service guide How to Prune Trees, which should the arborist address first?
Show answer and explanation
Correct answer: C. The broken hanging limb, since it could fall and injure someone
The USDA guide sets a clear order: prune first for safety, then for health, and last for aesthetics. A broken limb hanging over a sidewalk is a safety hazard, so it comes first. The rubbing branches are a health concern to handle next, and evening out the lopsided crown is an aesthetic goal that comes last.
- A: Rubbing branches are a health issue, which the guide ranks after safety.
- B: Crown balance here is an aesthetic objective, the lowest of the three priorities.
- D: The guide ranks the objectives in order rather than treating them as equal.
Source: How to Prune Trees (NA-FR-01-95, revised 2012), USDA Forest Service, Northeastern Area State and Private Forestry
Report a problem with this question · ID prun-001
Which tissue carries sugars made by photosynthesis from the leaves down to the roots and other growing parts of a tree?
Show answer and explanation
Correct answer: C. Inner bark (phloem)
The inner bark is the phloem, the tissue that moves sugars from the leaves to the roots and to other growing parts of the tree. Sapwood is the tempting wrong answer because it also conducts, but it carries water and dissolved minerals upward from the roots. Heartwood no longer conducts, and the outer bark protects the tree rather than transporting food.
- A: Sapwood conducts water and minerals up from the roots, not sugars from the leaves.
- B: Heartwood is the non-conducting core of the trunk.
- D: Outer bark protects the inner tissues and limits water loss; it does not move sugars.
Source: Wood Handbook: Wood as an Engineering Material (FPL-GTR-190), Chapter 3: Structure and Function of Wood, USDA Forest Service, Forest Products Laboratory
Report a problem with this question · ID bio-001
In tree risk management, who is responsible for deciding how much risk is acceptable and which mitigation, if any, will be carried out?
Show answer and explanation
Correct answer: B. The tree owner or manager
A risk assessor estimates the likelihood and consequences of failure and recommends options, but the tree owner or manager (for public land, the responsible official) decides what level of risk to accept and what work, if any, to do. The assessor is the tempting choice because they rate the risk, yet rating a risk and accepting it are separate roles. Work crews carry out decisions rather than make them, and an insurer does not manage the tree.
- A: The assessor evaluates the risk and recommends options but does not set the owner's risk tolerance.
- C: The crew carries out the chosen work; it does not decide what risk is acceptable.
- D: The owner or manager, not an insurer, is responsible for managing the tree.
Sources: Tree Risk Assessment Methods: A Comparison of Three Common Evaluation Forms (ENH1226), UF/IFAS Extension (EDIS) ; Field Guide for Hazard-Tree Identification and Mitigation on Developed Sites in Oregon and Washington Forests (R6-NR-TP-021-2013), USDA Forest Service, Pacific Northwest Region (GovInfo)
Report a problem with this question · ID risk-001
Which is the correct way to write the scientific name of northern red oak in a written report?
Show answer and explanation
Correct answer: C. Quercus rubra: genus capitalized, epithet lowercase, both in italics
A scientific name is a binomial made of the genus followed by the specific epithet. The genus is capitalized, the epithet is written in lowercase, and the whole name is italicized (or underlined when italics are not available). Capitalizing the epithet is a common error, and writing the name in plain type or all capitals breaks the convention.
- A: The specific epithet is always lowercase.
- B: The genus must be capitalized, and the name should be italicized or underlined.
- D: Only the first letter of the genus is capitalized, and the whole name should be italicized or underlined.
Sources: Extension Gardener Handbook, Chapter 3: Botany, NC State Extension ; Extension Gardener Handbook, Chapter 3: Botany, NC State Extension
Report a problem with this question · ID ids-004
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Eligibility requirements
ISA requires at least three years of full-time practical experience in arboriculture, or a combination of education and experience. One year of full-time work counts as about 1,795 hours. The accepted paths are:
- Three years of full-time practical experience in arboriculture
- Two-year associate degree with at least two arboriculture-related courses, plus two years of full-time experience
- Four-year bachelor's degree with at least four arboriculture-related courses, plus one year of full-time experience
- 900 hours of assessed training (at least 90 hours directly related to arboriculture), plus two years of full-time experience
- 1,800 hours of assessed training (at least 180 hours directly related to arboriculture), plus one year of full-time experience
- Approved registered or recognized apprenticeship programs may be accepted as equivalent
Qualifying work includes pruning, fertilization, planting and establishment, diagnosis and treatment, cabling and bracing, climbing and similar tree care, at employers such as tree care companies, nurseries, landscape firms, municipalities, utilities and consultancies. You submit proof with the application, such as reference letters from employers. Self-employed applicants provide three references, which can be invoices, contracts or business licenses.
Step-by-step: how to become an ISA Certified Arborist.
Fees
| Fee | ISA member or credential holder | Everyone else |
|---|---|---|
| Application | $40 | $50 |
| Exam enrollment | $295 | $369 |
| Retake | $120 | $120 |
| Reschedule outside your 120-day window | $50 | $50 |
| Recertification (continuing education route) | $220 | $220 |
All amounts in US dollars, from the ISA Program Guide (checked October 19, 2026). ISA members and credential holders get a 20% discount on application and enrollment fees. ISA does not refund exam enrollment fees, and missing your appointment forfeits them.
How to apply and schedule
- Create or sign in to your account on ISA's credentialing site and submit the Certified Arborist application with your experience documents.
- ISA reviews applications within five US business days and emails you the result.
- Once approved, enroll in an exam and pay the enrollment fee. Choose a computer-based exam at a Pearson VUE center or a paper exam with a local ISA Certification Partner.
- For the computer-based exam you get a 120-day window to schedule and sit it. You can reschedule inside that window at least one US business day ahead at no cost.
- On exam day, arrive 30 minutes early with two IDs: a photo ID and an ID showing your signature.
Passing score and results
The current passing score is 76% overall. Domains are weighted, so your domain scores won't average to your overall score. Computer-based candidates see a result on screen as soon as they finish; formal results are posted to your ISA account within four weeks. ISA does not release the questions or tell you which ones you missed, only your score report.
Retakes
If you don't pass, you can sit the exam again 30 days after your last attempt. Each retake costs $120, on paper or computer. See every fee with worked totals.
Recertification
Certification is valid for three years. To keep it, either pass the exam again or earn at least 30 continuing education units (CEUs) related to the ten exam domains during those three years and pay the $220 recertification fee. Our CEU guide explains how ISA counts CEUs and the deadlines.
Pass rate
ISA does not publish an official pass rate for the Certified Arborist exam in its Program Guide, and we have not found one on ISA's site (checked October 19, 2026). Some websites quote a figure without a source; we don't. What is published is the 76% passing score, which is the number to aim above. More on that in how hard the exam is.
How to prepare
Our free study guide has an 8-week plan and notes for every domain. In short:
- Read the official material. ISA publishes its own study guide for this exam, the Arborists' Certification Study Guide. We recommend it; our questions are written independently and are a complement, not a replacement.
- Practice by domain. Start with the heaviest domains and your weakest topics. Our free practice test has questions for every domain.
- Review every miss. Read why the right answer is right and why yours was wrong, then retest a few days later.
- Take timed mock exams. Sit at least two full 200-question mocks under the 210-minute clock before exam day.
- Close the gaps. Use your score by domain to decide what to study in the final week.
Questions about the exam
How many questions are on the ISA Certified Arborist exam?
The exam has 200 multiple-choice questions with four answer choices each, and you get 3.5 hours (210 minutes). 20 of the questions are unscored trial questions mixed in with the rest, so 180 questions count toward your score. Source: ISA Certified Arborist Program Guide, checked October 19, 2026.
What is the passing score for the ISA Certified Arborist exam?
The ISA Certified Arborist Program Guide lists the current passing score as 76 percent. It is an overall score: the ten domains are weighted, so your domain results will not simply average to your overall score.
What is the pass rate for the ISA Certified Arborist exam?
ISA does not publish an official pass rate in its Program Guide, and we have not found one anywhere on ISA's site (checked October 19, 2026). Be wary of sites that quote a specific figure without a source.
How much does the ISA Certified Arborist exam cost?
According to the ISA Certified Arborist Program Guide, the application fee is $40 for ISA members and credential holders or $50 for everyone else, and the exam enrollment fee is $295 for members or $369 for non-members. A retake costs $120. ISA does not refund exam enrollment fees.
What are the requirements to take the ISA Certified Arborist exam?
You need at least three years of full-time practical experience in arboriculture, or a combination of education and experience: for example, a two-year degree with arboriculture courses plus two years of experience, or a four-year degree with arboriculture courses plus one year. See our step-by-step guide for every path.
Can I take the ISA Certified Arborist exam online?
ISA offers the exam on computer at Pearson VUE test centers and on paper through local ISA Certification Partners. After enrolling for the computer-based exam you have a 120-day window to schedule and sit it. The Program Guide does not describe an at-home online option.
What happens if I fail the ISA arborist exam?
You can retake it 30 days after your last attempt. The retake fee is $120, whether you test on paper or by computer (ISA Certified Arborist Program Guide). If you bought Complete Prep, our pass guarantee also extends your access by 12 months for free while you prepare for the retake.
How long does ISA Certified Arborist certification last?
Three years. To keep it you either pass the exam again or earn at least 30 continuing education units (CEUs) in the tested domains during the three years and pay a $220 recertification fee (ISA Certified Arborist Program Guide).
Official sources
- ISA Certified Arborist Program Guide (revised August 2025)
- ISA Certified Arborist Examination Outline (based on Job Task Analysis 2022)
This guide summarizes ISA's published rules in our own words. It is not an official ISA document. If anything here differs from ISA's current documents, ISA's documents win.