WSIB Claim Denied? How to Appeal in Ontario (2026)

A denial is not the end. Many WSIB decisions are overturned on appeal—but only if you act fast.

You have just 30 days from a WSIB decision to request an internal review (ARO). Miss that window, and you lose your first appeal option entirely.

The good news? Ontario's appeal system gives you multiple chances to challenge an unfair decision. This guide shows you exactly how to navigate each stage, what evidence you need, and how to build the strongest possible case.

Understanding Why Claims Get Denied

Before appealing, understand why WSIB denied your claim. Common reasons include:

• Insufficient medical evidence linking your injury to work
• Late reporting of the injury to your employer
• Pre-existing condition not clearly distinguished from the workplace injury
• Disputed work-relatedness where WSIB questions whether the injury happened at work
• Missing documentation or incomplete forms

Review your denial letter carefully. The specific reason guides what evidence you need to gather.

Step 1: Request an Internal Review (ARO)

Deadline: 30 days from the decision date

Your first step is requesting an internal review handled by an Appeals Resolution Officer (ARO). This is a fresh look at your case by someone who wasn't involved in the original decision.

How to Request ARO Review

• Call WSIB or submit a written request
• Clearly state you want the decision reconsidered
• Identify which decision you're appealing

Strengthen Your Case

When preparing for the ARO review:

• Provide new medical evidence or specialist opinions
• Include witness statements from coworkers
• Submit additional documentation addressing the denial reason
• Write a clear letter explaining why you disagree with the decision

The ARO will review your case and issue a new decision. This may uphold, modify, or reverse the original decision.

Step 2: Appeal to WSIAT

Deadline: 6 months from the ARO decision

If the ARO decision is still unfavorable, you can appeal to the Workplace Safety and Insurance Appeals Tribunal (WSIAT). This is an independent body, separate from WSIB.

The WSIAT Process

1. File a Notice of Appeal online or by mail
2. Case preparation where WSIAT obtains your WSIB file
3. Hearing scheduled which may be in-person, by phone, or video
4. Written decision issued after the hearing

WSIAT hearings are more formal than internal reviews. The Tribunal considers your evidence, WSIB's position, and relevant law and policy.

Evidence Gathering Tips

Strong evidence makes or breaks appeals. Consider gathering:

• Updated medical reports with clear opinions on work-relatedness
• Specialist assessments from orthopedic, neurological, or psychological experts
• Witness statements from coworkers who saw the incident or your working conditions
• Employment records documenting your job duties
• Photos or videos of the workplace
• Your complete WSIB file to understand what evidence they relied on

Request your WSIB file early. This shows exactly what information was used in the decision.

Key Deadlines

Missing these deadlines can eliminate your right to appeal. Mark them on your calendar immediately when you receive a decision.

When to Get Professional Help

Consider working with a representative if:

• Your case involves complex medical issues
• You've been denied at both the initial and ARO levels
• Significant lost income is at stake
• You're uncomfortable presenting your own case
• The legal or policy issues are complicated

Licensed paralegals, lawyers, and some union representatives specialize in WSIB appeals and can significantly improve your chances of success.

Don't Face Your Appeal Alone

Appealing a WSIB decision is stressful—especially when you're already dealing with an injury. Missing a deadline or forgetting a document can set you back weeks.

ClaimNexus keeps your appeal on track:

• 30-day deadline alerts – Never miss the ARO window
• All documents organized – Evidence, medical reports, correspondence in one place
• AI-powered guidance – Understand WSIB policies without legal jargon
• Preparation checklists – Know exactly what you need before each stage

Your information stays private. We're not affiliated with WSIB.

Start organizing your appeal →

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This guide provides general information about the WSIB appeals process. For advice specific to your situation, consult a licensed paralegal, lawyer, or your union representative. This is not legal advice.