What is a Certified Arborist?

Certified Arborist explained

ISA Certified Arborist® is a voluntary credential issued by the International Society of Arboriculture (ISA), the largest credentialing body for arborists in the world.

To qualify, a candidate needs at least three years of full-time arboriculture experience — or a documented mix of education and experience, such as a two-year degree plus two arboriculture courses and two years on the job, or a four-year degree plus four courses and one year on the job.

Candidates must sit a 200-question multiple choice exam covering little bits of every aspect of the industry. Candidates must score 76% or greater to pass. The credential lasts three years; to maintain the credential arborists must complete 30 continuous education units every 3 years as well as pay a renewal fee.

When you see a Certified Arborist credit on a listing here, it’s because we found that specific person by name in ISA’s own public arborist directory.

Benefits of a Certified Arborist

It sets a baseline. Rather than a company simply calling itself “expert,” the credential shows an independent body actually tested the person’s knowledge against a standardized bar.

It’s a common language. A Certified Arborist means roughly the same thing wherever you see it, in Ontario or anywhere else ISA operates, rather than every company defining the term for itself.

It has to be kept current. Because the credential expires every three years, an active one means the person has kept learning — not that they passed a test once and stopped.

Anyone can access this arborist directory through ISA’s website www.treesaregood.org to see a complete list of every Certified Arborist and Board Certified Master Arborist.

Limitations of a Certified Arborist

It’s not a license. ISA’s own program materials are explicit that the credential does not represent licensure, registration, or authorization to conduct business. Ontario has no licensing system for arborists at all, so this credential is not a substitute for one.

It doesn’t guarantee the work performed. The exam tests knowledge, not on-the-job judgment, safety culture, or how a specific crew handles a specific job.

The exam itself is multiple choice, so it does not test a candidate’s hands-on ability to carry out proper tree care.

It’s a standardized international exam, so it doesn’t test the regulations, tree species, or pest concerns unique to any one region. It’s not correct to assume a Certified Arborist is familiar with local or site-specific concerns just because they hold the credential.

It says nothing about insurance or WSIB coverage. Those are entirely separate — a company can employ a Certified Arborist and still lack either.

It’s one person, not the whole crew. A company might have a single Certified Arborist on staff while most of the actual climbing and cutting is done by others without the credential. It’s worth asking specifically who on your job will hold it, and for what part of the work.