What are Vendor Due Diligence Reviews?

Before you onboard a vendor, you need to know exactly what you’re signing up for.

Vendor relationships can drive innovation, efficiency, and growth — but they also introduce risk. Vendor due diligence reviews are critical to protecting your organization, customers, and reputation. These reviews help you understand a vendor’s risk profile by analyzing its documentation and the effectiveness of its controls, ensuring the relationship aligns with your organization’s needs and standards.

In this blog, we’ll break down what vendor due diligence reviews are, how they work, and how to make them scalable, strategic, and risk based. 

What are Vendor Due Diligence Reviews? 

Vendor due diligence reviews are targeted evaluations where an organization examines a vendor’s documentation — such as policies, SOC reports, financials, and business continuity plans — to determine if the vendor’s control environment effectively addresses and mitigates the risk posed to your organization. These reviews occur both before signing a contract and periodically throughout the relationship to ensure the vendor continues to meet your requirements over time.

Vendor due diligence reviews are the analytical heart of vendor oversight. After gathering questionnaires, responses, and supporting documents through the vendor due diligence process, the organization digs into the details to assess whether the vendor’s controls are sufficient, identify potential gaps, and determine what risks remain.  

The results of these reviews help drive risk ratings, remediation plans, contract negotiations, and ongoing monitoring strategies throughout the vendor relationship. 

Related: What to Do with Vendor Due Diligence Information 

Vendor Due Diligence Reviews vs. the Vendor Due Diligence Process

It’s important to distinguish vendor due diligence reviews from the broader vendor due diligence process.

The vendor due diligence process is the overall framework for gathering and assessing vendor risk information before and during the relationship. It includes steps like sending questionnaires, collecting documentation, and establishing baseline risk profiles.

Vendor due diligence reviews, however, are the specific evaluation and analysis activities within that process. A review is when your team — typically subject matter experts — examines the documentation to validate that the vendor’s controls, practices, and risk posture align with your organization’s expectations. 
 

How to Perform Vendor Due Diligence Reviews 

Once vendor questionnaires, responses, and supporting documentation are collected, the vendor due diligence review begins.

The review is a focused, methodical evaluation of whether the vendor’s controls and practices align with your organization’s risk, compliance, security, and performance standards. 

A strong vendor due diligence review involves several key steps: 

• Organize the documentation – Before diving into analysis, ensure all required materials have been received and are complete. Missing, outdated, or incomplete documents should be flagged immediately for follow-up, as a review is only as strong as the evidence being evaluated. 
• Use subject matter experts (SMEs) to review documentation – SMEs should evaluate each control, policy, or certification within their areas of expertise against your organization’s expectations and regulatory requirements. For example, cybersecurity SMEs might assess firewall management practices and incident response plans, while financial SMEs review audited financials for signs of instability. The review must consider whether documentation is current, complete, and reflects strong, tested practices. 
• Analyze for sufficiency and gaps – It’s not enough to confirm that a policy or control exists — the review must determine whether it is robust enough to address the vendor’s inherent risks. Are controls tested regularly? Are certifications recent? Does the documentation demonstrate a mature risk management program or minimal compliance? 
• Document findings clearly and objectively – A thorough review produces more than a checklist. It should document strengths, deficiencies, uncertainties, and recommendations. Findings must tie back to the vendor’s overall risk profile and the potential impact on your organization. 
• Summarize the vendor’s risk posture – Based on the review, determine whether additional due diligence is needed, whether mitigation strategies should be considered, or whether the vendor presents an acceptable risk given the controls in place. The summary helps inform decisions about risk acceptance, contract structure, and monitoring requirements. 

The vendor due diligence review doesn’t solve problems — it shines a light on them, providing the critical information needed to support decisions about vendor selection, oversight, and risk management. 

Related: Identifying and Documenting Third-Party Risk Management Issues 

5 Tips for Strong Vendor Due Diligence Reviews 

Vendor due diligence reviews are only as strong as the approach behind them. Tightening the review process makes evaluations more effective, consistent, and risk driven.

Here’s how to improve your vendor due diligence reviews: 

• Evaluate depth based on risk, not just presence of documents — A strong review doesn't just confirm that a document exists; it assesses how thoroughly the document addresses relevant risks. High-risk and critical vendors require deeper analysis of policies, controls, and certifications, while lower-risk vendors may be evaluated with lighter touchpoints. 
• Use SMEs strategically, not uniformly — Assign SMEs where specialized expertise adds real value. Focus their time on areas of risk that matter most for each vendor relationship. Not every document needs the same level of SME scrutiny — align review depth with the vendor’s risk profile and the materiality of the service. 
• Track review outcomes systematically — Every vendor due diligence review should feed into a structured findings report or risk summary. Capture observations, gaps, and recommendations in a standardized way to inform downstream decisions about remediation, monitoring, and overall vendor management. 
• Keep review criteria and expectations current — Risk environments shift. Review templates and criteria should evolve with changes in regulatory expectations, cybersecurity threats, financial instability trends, and emerging best practices. Regularly recalibrate what constitutes "sufficient" documentation or controls during reviews. 
• Outsource reviews when needed — If your organization lacks the internal expertise or capacity to thoroughly review certain high-risk vendors, consider outsourcing to qualified third-party experts. Outsourcing specialized reviews — such as cybersecurity, financial health, or business continuity assessments — can strengthen your due diligence without overburdening internal teams. 

Short on time or expertise? Learn how Venminder’s Vendor Control Assessments can help support your third-party risk management efforts.  

Vendor due diligence reviews are critical for maintaining a clear, accurate understanding of vendor risks throughout the life of a relationship. Strong reviews protect your organization and customers, reduce exposure to third-party risks, and build stronger, more resilient vendor partnerships. 

Learn how to perform vendor due diligence reviews on  
six of the most common due diligence documents in our free guide  
How to Do Vendor Due Diligence Reviews: The Complete Breakdown.