An ISA Certified Arborist is a tree-care professional who has passed the International Society of Arboriculture’s 200-question exam after at least three years of full-time arboriculture experience (or an approved mix of education and experience), and who must recertify every three years. It is a voluntary credential, not a government licence, so in Toronto you should verify it yourself before you rely on it.
This page covers the credential itself: what it proves, how it compares with other arborist credentials you will meet in Ontario, and how to check one in a few minutes. For the full hiring process (quotes, insurance, permits, red flags), see our guide on how to hire a certified arborist in Toronto.
What ISA Certified Arborist Means
The International Society of Arboriculture (ISA) describes its certification as a voluntary program that tests a professional level of knowledge and skill in arboriculture. According to ISA’s Certified Arborist program guide, the credential involves:
- Experience: a minimum of three years of full-time arboriculture experience, or a combination of education and practical experience. ISA counts one year of full-time work as roughly 1,795 hours.
- An exam: 200 multiple-choice questions, four answers each, with 3.5 hours to finish. It covers 10 tested domains, from tree biology and diagnosis to maintenance and safety.
- A code of ethics: every holder agrees to the ISA Code of Ethics and a credentialing agreement.
- Recertification every three years: either by passing the exam again or by earning at least 30 continuing education units (CEUs) in that period.
The recertification rule is the part homeowners often miss. A certificate that lapsed years ago is not the same as a current one, which is why the verification step below matters.
What the Credential Does and Does Not Guarantee
ISA is direct about the limits. Its program guide says certification holders have demonstrated “an internationally accepted fundamental level of knowledge and skills” and that “no other conclusions may be drawn.” It also states that ISA certifications do not represent licensure, registration or authorization to do business.
In practical terms, an ISA Certified Arborist credential tells you the individual has passed a standardized knowledge test and is bound by a code of ethics. It does not tell you:
- that the company they work for carries liability insurance or that its crew is covered by WSIB;
- that the person standing in your yard is the credential holder (a company can advertise one certified person while untrained workers do the cutting);
- that the company will follow Toronto’s permit rules, or file the paperwork for you;
- what the job will cost or whether the quote is fair.
Treat the credential as a strong first filter on knowledge, then check insurance, quote quality and permits separately. The hiring guide walks through each of those checks.
ISA Certified Arborist vs Other Credentials in Ontario
Searches for an “arborist credential” turn up several different things. They are not interchangeable.
| Credential | Issued by | What it shows | Key facts (from the issuer) |
|---|---|---|---|
| ISA Certified Arborist | ISA | Broad arboriculture knowledge: biology, diagnosis, maintenance, safety | Voluntary; 200-question exam; valid three years; recertify by exam or 30 CEUs |
| ISA Board Certified Master Arborist | ISA | An advanced level of the same knowledge base | Open only to current ISA Certified Arborists who meet a points-based experience, education and credential threshold; exam covers 17 domains; valid three years; recertify by exam or 60 CEUs |
| ISA Tree Risk Assessment Qualification (TRAQ) | ISA | A trained, tested method for assessing the risk a tree poses | Voluntary qualification; requires a training course plus written and performance-based assessments; holders retrain and retest every seven years |
| Arborist trade Certificate of Qualification | Skilled Trades Ontario | Trade competency under Ontario’s apprenticeship system | Non-compulsory trade; about 6,120 hours (5,400 on the job plus 720 in school); certifying exam |
ISA Board Certified Master Arborist
The Master Arborist credential is a step above the Certified Arborist. You must already be a Certified Arborist in good standing, and ISA’s current guide sets a passing score of 70 percent. It is a useful signal for complex consulting work, but you do not need it to remove a backyard tree safely.
ISA TRAQ
TRAQ is the one to look for when the question is “is this tree dangerous?” It trains and tests professionals in a standardized way of assessing tree risk, so it is relevant to storm-damaged, leaning or decayed trees, and to risk write-ups for insurers. ISA lists the Certified Arborist and Master Arborist credentials among those that make a candidate eligible to enrol. When you need a written risk opinion, ask whether the arborist holds TRAQ and which risk method the report uses. Our hazardous tree removal page explains what a risk-based removal involves.
Ontario’s Arborist trade certification
Skilled Trades Ontario’s Arborist trade is non-compulsory, which means nobody is legally required to hold it to work as an arborist in Ontario. This is why the phrase “licensed arborist” can mislead: there is no mandatory provincial licence. Skilled Trades Ontario also states that individuals practising this trade do not appear on its Public Register, so you cannot look someone up there. If an arborist says they hold a Certificate of Qualification, ask to see the certificate.
How to Verify an ISA Credential
- Ask for the full name and the exact credential. “Certified arborist” alone is not enough. You want the name of the person and the name of the credential (for example, ISA Certified Arborist or TRAQ).
- Use ISA’s own search. ISA’s For the Public page links to a Find an Arborist tool described as a way to locate an arborist or verify a credential. Search the name and confirm the credential and its status.
- Check that the credential is current. Because holders recertify every three years, look for an active status rather than a historical listing.
- Ask for the certificate or digital badge if the search shows nothing. Listings depend on how the holder registered, so a missing result is a reason to ask a follow-up question, not proof of fraud. ISA lists digital badges among its credential resources.
- Confirm who will be on site. Ask which certified person will assess the tree, sign any report and supervise the crew.
The whole check takes a few minutes, and a reputable company will not mind it.
When the Credential Matters Most in Toronto
For a small, healthy tree, a competent crew and the right insurance may be all you need. The credential becomes important in these situations:
- Permits. Toronto’s private tree by-law (Municipal Code Chapter 813) requires a permit for trees with a trunk diameter of 30 cm or more, and the City’s removal application calls for a report from an arborist. Fines for unpermitted removal run from $500 to $100,000 per tree. See our Toronto tree removal permit guide.
- Risk and insurance. If a tree is split, leaning or storm-damaged, a written assessment by a credentialed arborist carries more weight than a verbal opinion.
- Construction and property sales. Condition reports for planned work or a sale are produced by arborists. Read about arborist reports.
- Disputes over whether a tree needs to go. A neutral written assessment can settle a disagreement with a neighbour, condo board or insurer.
The City’s measurement rule is worth knowing: diameter is measured 1.4 metres above ground, and for a multi-stem tree, if any one stem reaches 30 cm the whole tree is protected.
Our Team’s Credentials
Our lead arborists hold ISA certification. We carry $5,000,000 in general liability insurance and our crew is WSIB-covered, and certificates of insurance are available on request before work begins. You can read our company details on the facts page. Ask us who would assess your tree and we will tell you before you book. For a no-obligation written quote, use the contact page or call 647-558-1366.
For a plain-language overview of costs and the removal process itself, our Toronto tree removal guide is the place to start.
Frequently Asked Questions
What is an ISA Certified Arborist?
An ISA Certified Arborist has passed the International Society of Arboriculture’s 200-question exam after at least three years of full-time arboriculture experience, or an approved combination of education and experience. The credential is voluntary and must be renewed every three years.
Is an ISA Certified Arborist the same as a licensed arborist in Ontario?
No. ISA certification is issued by a professional society and does not represent licensure. Ontario’s Arborist trade is non-compulsory, so there is no mandatory provincial licence for arborists. Skilled Trades Ontario also does not list people practising this trade on its Public Register.
How do I check that an arborist is really ISA certified?
Get the person’s full name and exact credential, then search ISA’s Find an Arborist tool, which is linked from ISA’s For the Public page. Confirm the credential is current, and ask for the certificate or digital badge if nothing appears.
What is the difference between ISA Certified Arborist and TRAQ?
Certified Arborist is a broad credential covering many areas of tree care. TRAQ is a specialized qualification in tree risk assessment that requires a training course and both written and performance-based assessments, and holders retrain and retest every seven years.
Does an ISA credential mean the company is insured?
No. The credential applies to an individual’s knowledge, not to a company’s insurance. Ask for proof of liability insurance and WSIB coverage separately before any work begins.
Do I need a certified arborist to remove a tree in Toronto?
If the trunk is 30 cm in diameter or larger, you need a permit under Toronto Municipal Code Chapter 813, and the City’s removal application asks for a report from an arborist. Fines for unpermitted removal range from $500 to $100,000 per tree.