Background/Objectives: In Canada, understanding the connection between substance use, help-seeking behaviors, and mental health (MH) is crucial for improved public health outcomes. Despite advances in MH services, gaps persist in addressing unmet needs of substance users. Methods: Utilizing data (N=3,910) from the 2020 Canadian Perspectives Survey, and employing logistic regression models, this study assessed the impact of unmet help needs (UHNs) on MH of substance users. Results: The findings indicate that individuals who experienced UHNs for substance use (OR=0.196; P<0.001) significantly reported lower odds of Positive Mental Health (PMH). Non-prescription drug users (OR=0.585; P<0.001), weekly (OR=0.544; P<0.05) and daily cannabis users (OR=0.605; P<0.05), as well those who felt uncomfortable seeking substance-use related help (OR=0.595; P<0.001), all reported lower odds of PMH. Conclusions: The use of non-prescription drugs, frequent cannabis consumption, experience of UHNs, and discomfort in seeking help for substance use are significantly associated with lower odds of PMH. Thus, accessible, stigma-free and timely MH and harm reduction services are crucial for promoting PMH among substance users in the study context.