ISA Certified Arborist: What the Credential Requires

A 2026 Reality Check: ISA Certified Arborist

Short answer: ISA Certified Arborist requires three years of documented arboriculture experience (less with a relevant degree), a 200-question exam across 10 knowledge domains, and a 76 percent passing score ^[S1]. It expires every three years unless the holder retests or logs continuing education. You can verify anyone’s credential for free through ISA’s own lookup tool ^[S2].

Sources for this table: S1, S2 in the Sources list below.

What it actually takes to become a certified arborist

ISA does not hand out this credential for showing up. A candidate needs three years of full-time, documented experience in arboriculture before they can even sit for the exam, or a shorter experience window paired with a two- or four-year degree in a related field ^[S1]. That experience requirement alone filters out most weekend operators. ISA treats the credential as ongoing proof, not a one-time badge, which is exactly why the renewal rules below matter as much as the exam itself ^[S3].

The application also asks for professional references and a signed code of ethics, not just a fee and a test date. ISA built the program this way on purpose: the goal is a credential that means the same thing whether the person holding it works in Ohio or Oregon.

The exam: ten domains, one passing score

The exam itself runs 200 multiple-choice questions, and it’s not a formality. Candidates answer across ten knowledge domains, including tree biology, soil science, diagnosis and treatment, pruning, tree risk, and safe work practices, and need a 76 percent score to pass ^[S1]. Someone who can only talk about pruning, without understanding root systems or how a stressed tree fails, will not clear that bar.

That breadth matters more than it looks on paper. A crew that only knows how to drop a tree can still get a big job done wrong: misdiagnosing a root problem, cabling a tree that should have come down, or pruning in a way that invites disease. The exam exists to catch exactly that gap before it shows up on your property.

Renewal: why the letters can expire

Certification is not a one-time achievement. It expires after three years, and keeping it active means either retaking the exam or accumulating continuing education credits spread across those same ten domains ^[S1]. That renewal cycle is the whole point of the credential still meaning something: a card printed in 2016 with nothing behind it since is not the same as one backed by a decade of ongoing training.

Ask when someone’s certification was last renewed, not just whether they hold it. A lapsed or expired credential is a legitimate red flag worth a direct question, not an assumption.

How to verify one before you hire

Anyone can claim the title. Only ISA’s own records confirm it’s real. Ask for the certification number and run it through ISA’s free “Find an Arborist” verification tool, which confirms current status by name or number in seconds ^[S2]. UF/IFAS Extension gives homeowners the same advice: before picking an arborist, go straight to that same ISA lookup site and verify the credential yourself rather than taking a company’s word for it ^[S5].

A legitimate certified arborist will hand over that number without hesitation, since it costs them nothing to prove. Hesitation, a vague “we’re all trained,” or a certification that turns up expired on lookup are the clearest signals to keep shopping. See how to choose a tree service for the rest of the listing checks checklist beyond the credential itself.

The tier above: Board Certified Master Arborist

Certified Arborist is the base credential; Board Certified Master Arborist (BCMA) sits above it, and a candidate must already hold Certified Arborist status before they’re even eligible to add the points from experience, education, or other credentials that BCMA requires ^[S1]. Most routine jobs don’t need a BCMA on site. See what is an arborist for the full comparison between the two tiers.

Why hiring a certified arborist matters

TCIA-Accredited companies must keep the required number of Certified Arborists on staff, on top of maintaining insurance and a documented safety program, which is a useful floor for what a real tree care business looks like ^[S4]. A crew without a single certified arborist on staff can still do fine work on routine trimming, but it’s a bigger gamble the larger, riskier, or more valuable the tree gets.

Certified arborists tend to cost more than an uncertified crew for the same job, since the credential reflects real training and liability the company carries. That liability angle runs both ways: an arborist running their own outfit needs the right coverage too, and our arborist insurance guide covers what a solo or small operation should actually carry. LawnStarter’s national average for professional tree trimming, certified crew or not, runs $430 to $640 per tree, and a certified operation typically sits toward the higher end of published ranges like that one ^[S6]. See the tree trimming cost guide for the full breakdown, or the tree removal cost guide for removal pricing by size and access. Every pro in our directory has already cleared our listing checks checklist, so you’re screening between qualified crews, not gambling on a stranger’s word.

Key takeaways

• Certified Arborist requires three years of documented experience (less with a relevant degree) plus a 200-question, 10-domain exam ^[S1].
• The passing score is 76 percent, and the credential expires every three years without renewal ^[S1].
• Renewal means retesting or logging continuing education credits across the same ten domains ^[S1].
• Always verify a credential number through ISA’s own free lookup tool before you sign anything ^[S2].
• TCIA-Accredited companies must keep the required number of certified arborists on staff, a useful gut check for real tree care businesses ^[S4].

Frequently asked questions

What does it take to become a certified arborist?

A candidate needs three years of full-time arboriculture experience, or a shorter window combined with a related degree, before they can sit for the exam. They also pass a 200-question test across 10 knowledge domains with a 76 percent score ^[S1].

How do I verify someone is actually a certified arborist?

Ask for their ISA credential number and run it through ISA’s free “Find an Arborist” verification tool, which confirms current status by name or number ^[S2]. A real credential holder hands that number over without hesitation.

Does the certified arborist credential expire?

Yes. It expires every three years unless the holder retakes the exam or logs continuing education credits across the same knowledge domains ^[S1]. A stale, unrenewed credential from years ago is not the same guarantee as an active one.

Is Board Certified Master Arborist better than Certified Arborist?

It’s a more advanced tier built on top of it, requiring points from added experience, education, or other credentials before a candidate can even sit for the BCMA exam ^[S1]. Most residential jobs only need a standard Certified Arborist; BCMA matters more on complex or high-value trees.

Do I need a certified arborist for a small pruning job?

Not always. Light, low pruning on a small, healthy tree is often fine with an experienced, uncertified crew. Diagnosis, removal near a structure, cabling, or anything involving a dispute or insurance claim is where a certified arborist earns their fee.

Does hiring a certified arborist cost more?

Usually, yes, since the credential reflects real training and the company’s added liability. See the tree trimming cost guide and tree removal cost guide for what that work runs by size and access.

A job that calls for a certified arborist usually shows it in the details: measuring DBH before quoting a per-inch price, choosing crown reduction over a flush cut, and picking rigging or drop-cutting based on clearance, with crane-assisted removal held in reserve for anything too close to a structure for either. A wood chipper and a bucket truck are standard equipment on a real crew, and cabling and bracing comes up on any valuable tree worth saving instead of removing. None of it should start without a certificate of insurance covering general liability and workers’ comp, an 811 call before digging, and a city tree permit where a local heritage or protected tree ordinance applies. The work itself follows ANSI A300 pruning standards and ANSI Z133 safety rules, the same framework OSHA references for the tree care industry, and per-inch pricing usually comes with a minimum call-out fee on small jobs.

How we built this guide

We verified certification and renewal requirements directly against ISA’s own program guide and cross-checked hiring guidance against a university extension source. This guide cites 6 sources, , reviewed by the CompareTreeServices editorial team.

A certified arborist is not just a job title, it’s a tested credential with a real expiration date. Ask for the number, verify it through ISA, and confirm it’s current before you let anyone near a valuable or risky tree.

Sources

1. ^[S1] International Society of Arboriculture, “ISA Certified Arborist Program Guide”
2. ^[S2] International Society of Arboriculture, “Verify a Credential”
3. ^[S3] International Society of Arboriculture, “Why Get Certified”
4. ^[S4] Tree Care Industry Association, “TCIA Accreditation”
5. ^[S5] UF/IFAS Extension Lake County, “Do I Really Need an ISA Certified Arborist for Tree Work? How Do I Pick One?”
6. ^[S6] LawnStarter, “How Much Does Tree Trimming Cost?”