TREADSTONE LAW · ONTARIO · DIGITAL LEGAL SERVICES · EST. MMXXI ·TSL
Home/Articles/Corporate
№ 491 Corporate

When Ontario Employers Must Investigate a Harassment Complaint

Ontario's occupational health and safety law requires employers to investigate workplace harassment in specific circumstances. Here's when the duty kicks in.

Corporate5 min readTSLBy the Treadstone Law team · OntarioUpdated 2026-07
All articles
Key takeaways
  • Ontario's occupational health and safety framework covers workplace harassment broadly — generally understood as a course of vexatious comment or conduct that is known, or ought…
  • Ontario employers are generally required to have a written workplace harassment policy and a related program, and that program must set out how incidents and complaints will be investigated.
  • Ontario law doesn't prescribe one rigid investigation format for every complaint — the standard is generally that the investigation must be appropriate in the circumstances.

A lot of Ontario employers assume a harassment investigation is optional — something you do if a complaint feels serious enough, or if a lawyer gets involved. That's not how Ontario's Occupational Health and Safety Act treats it. Once certain conditions are met, investigating isn't a judgment call; it's a legal obligation.

Here's what actually triggers that duty, and what it does and doesn't require.

What Counts as Workplace Harassment Under OHSA

Ontario's occupational health and safety framework covers workplace harassment broadly — generally understood as a course of vexatious comment or conduct that is known, or ought reasonably to be known, to be unwelcome, along with workplace sexual harassment specifically. It can come from a manager, a coworker, or in some cases a third party like a client or customer.

A single, isolated comment doesn't always meet the legal threshold for "harassment" as defined, though it can still be worth addressing as a conduct issue. Whether a pattern of behaviour crosses into legally defined harassment is a fact-specific question.

The Legal Trigger for an Investigation

Ontario employers are generally required to have a written workplace harassment policy and a related program, and that program must set out how incidents and complaints will be investigated. In practical terms, once an employer receives a complaint of workplace harassment — or otherwise becomes aware of an incident that could constitute harassment — the obligation to investigate is engaged.

That means:

What "Appropriate in the Circumstances" Means

Ontario law doesn't prescribe one rigid investigation format for every complaint — the standard is generally that the investigation must be appropriate in the circumstances. What's appropriate scales with the seriousness of the allegation, the workplace, and the parties involved. A minor interpersonal complaint between two coworkers doesn't necessarily need the same process as an allegation involving a senior leader or a pattern of repeated conduct.

At a minimum, an appropriate investigation generally involves:

What Happens If an Employer Doesn't Investigate

Failing to investigate when the duty is triggered isn't just a policy failure — it's a compliance gap under occupational health and safety law, and it can also feed into other legal exposure:

A documented, appropriate investigation — even one that doesn't substantiate every allegation — is generally far better legal footing than no investigation at all.

A Practical Checklist

Frequently asked questions

Do I have to investigate every complaint, even minor ones?

Generally yes, in the sense that some form of response appropriate to the circumstances is required — but "appropriate" for a minor complaint can look very different from what's needed for a serious allegation. Ignoring a complaint entirely is the outcome to avoid.

Can I use an internal manager to investigate, or do I need an outside investigator?

Either can be appropriate depending on the circumstances. An external investigator is often the safer choice where there's a conflict of interest, a senior person is accused, or the allegations are serious.

What if the complaint turns out to be unfounded?

An investigation that concludes the allegations aren't substantiated still needs to be conducted fairly and documented. An unfounded outcome doesn't mean the investigation was unnecessary or that no obligation existed.

Does this apply to small employers too?

The general duty to have a policy, a program, and an investigation process applies broadly across Ontario workplaces, not just larger employers. Business size can affect how the investigation is resourced, but it doesn't remove the underlying obligation.

This article is general information, not legal advice. Reading it does not create a lawyer-client relationship. Ontario laws, tax rates, and government programs change, and how the law applies depends on your specific facts. For advice about your situation, speak with a licensed Ontario lawyer. Treadstone Law is licensed by the Law Society of Ontario — reach us at 1-844-900-1070 or start a file online.

This is a corporate question

Start a file online — flat, published fees, reviewed by a licensed Ontario lawyer before a dollar is owed.

ContactStart a File →