ArborProof

Fact-checking tree companies.

Is the Title of “Certified Arborist” Being Abused?

October 26, 2026 · By Aaron DeVos

A worker in a hi-vis vest cuts a branch from a spruce trunk with a curved pruning saw

Summary

Of the 524 companies in our directory, 100 claim to have a Certified Arborist that we couldn’t confirm. 35 of them show the ISA Certified Arborist badge without the name and badge number the ISA requires, which leaves homeowners no way to check the claim.

How do you know if you are hiring a Certified Arborist?

If you are basing your answer on what you find on a company’s website, you may be misled.

Scroll through website after website and you will find lines such as:

“Every project is overseen by an ISA Certified Arborist”
“Exceptional team of fully certified arborists on staff”
“Your local ISA certified tree service”
“Certified and licensed by the ISA”
“Proud to be an ISA Certified Arborist”

Those are actual quotes from some tree service companies in Ontario.

While website after website might state that they are Certified Arborists, is it actually true?

Of our directory of 524 companies, we found 100 companies where there was a claim to being a Certified Arborist but no evidence to prove it.

Ontario Arborist Companies and their Claims to being Certified ArboristsLast checked October 24th 2026Companies in our Ontario directoryCompanies in our Ontario directory: 524524Companies with a confirmed Certified ArboristCompanies with a confirmed Certified Arborist: 151151Companies with no confirmed Certified ArboristsCompanies with no confirmed Certified Arborists: 373373Companies that claim to have a CertifiedArborist but we couldn’t confirmCompanies that claim to have a Certified Arborist but we couldn’t confirm: 100100Companies that inaccurately showCertified Arborist badgeCompanies that inaccurately show Certified Arborist badge: 3535Companies that post an invalid badge numberCompanies that post an invalid badge number: 44
Directory homepage review, October 2026 · 524 companies, 373 scanned

And of those 100 companies, we found 35 that not only state that they are certified arborists but also show the exact same badge on their website to present themselves as Certified Arborists.

What the ISA requires

A little bit of background is in order. The organization that trademarked the Certified Arborist designation is the International Society of Arboriculture, best known by its acronym, the ISA. The ISA is the sole issuer of any form of a Certified Arborist badge. There is no competing government or non-government agency that also issues a Certified Arborist designation.

Anytime you see a Certified Arborist badge, it is a direct link to the International Society of Arboriculture.

Through our research, we found 35 companies that not only state they are certified arborists, but also show the trademarked Certified Arborist badge. And they show the badge wrong.

The ISA has strict stipulations surrounding how the badge is shown. Most notably, the badge must also display the first and last name of the certificate holder, as well as the badge number.

The ISA Certified Arborist logo with a sample name, Joe Arborist, and badge number printed beneath it, labelled 'first and last name' and 'badge number'

The ISA makes it clear that the badge cannot be shown on its own without the person’s name and badge number. You can read their exact rules at https://wwv.isa-arbor.com/styleGuide/ISA_BrandingGuide.pdf.

Why it matters

This is a problem for two reasons. First, if a company displays this badge, there is no way to check that company against the ISA online directory at https://www.treesaregood.org/ to see if the claim is true. The ISA lists certifications by people’s names, not by company. Searching the ISA by company name is a futile effort.

The second problem is that it conveys to the public that the whole company is certified. A company that posts the badge without listing a name could easily lead the public to think that the company as a whole has some form of certified arborist accreditation. That is simply not true; the ISA only grants certifications to individuals, not companies.

Here at ArborProof, we have worked very hard to link individual names to the companies they work for. As of the time of writing, we have confirmed 151 of the 524 companies in our directory to have an arborist with the Certified Arborist credential.

There is much more that could be said about this topic, but that will be left for another day, starting with this question: if so many companies are misusing the badge, why doesn’t the ISA crack down on it? In the meantime, the best protection is to check for yourself.

How to check before you hire

A real ISA Certified Arborist can be confirmed in just a few minutes.

  1. Ask for the arborist’s full name and ISA certification number (Ontario numbers look like ON-1234A).
  2. Look them up in the ISA’s Find an Arborist directory at TreesAreGood.org.
  3. Ask if a certified arborist will be involved in the sales appointment and in carrying out the actual tree work. It is ideal to have both these boxes checked.

Last edited on October 26, 2026