The ISA Certified Arborist exam: format, domains and pass mark
What's on the exam, how it's weighted and how to prepare, from ISA's published examination outline.
The 10 domains and their weights
ISA publishes the share of the exam given to each domain. Pruning and safe work practices together make up almost a third of the exam.
Who can take the exam
ISA requires three years of full-time, practical experience in arboriculture, or a two-year or four-year degree in arboriculture, horticulture, landscape architecture or forestry plus one or two years of experience. Rules and fees change, so check the current handbook on isa-arbor.com before you apply.
Standards on the exam
Many questions test the ANSI standards: A300 for tree care practices, Z133 for safety and Z60.1 for nursery stock. The current exam outline dates from 2022, before ANSI Z133-2026, so some questions may still use 2017 values. Our lessons teach the 2026 values and point out where the older ones differ.
Common questions
How many questions are on the Certified Arborist exam?
200 multiple-choice questions, each with four options. 180 are scored; the other 20 are unscored trial questions that ISA is testing for future exams, and you can't tell which ones they are.
How long is the exam?
3.5 hours (210 minutes). That's about a minute a question, so there's time to read carefully and review flagged questions at the end.
What score do I need to pass?
76% of the scored questions.
How should I study?
Work through the domains in order, drill each one, then sit a full mock exam under timed conditions. Review every question you got wrong, study your weakest domain, and sit the next mock exam a week later.
See how ready you are
Try 10 free sample questions, one from each domain, with the reason behind every answer.