Introduction: Although the well-being of Regular Force Veterans in Canada has been characterized, including aspects of their transition to civilian life and their mental health, there are few papers that investigate these characteristics in the Reserve Force. The objective of this research was to explore the association between demographic and service characteristics and mental health in Canadian Veterans of the Reserve Force. Methods: Participants of this research were part of the 2013 Life After Service Studies that included a sample of Veterans of the Reserve Force. These were Veterans of Reserve Force Class C (n = 905) and Reserve Force Class A/B (n = 465). Bivariate and multivariate analyses were carried out incorporating survey design to assess the association of 24 demographic and service variables on the Mental Component Score (MCS) for each group of Reserve Force Veterans. Two multivariate models were produced with a different number of variables related with MCS. Results: Seven variables remained statistically significant in the Reserve Force Class C model: marital status, age, chronic pain, depression, anxiety, posttraumatic stress disorder (PTSD), and type of release. The Reserve Force Class A/B model retained five variables: age, depression, anxiety, PTSD, and type of release. Discussion: These results showed that a similar group of variables were associated with the MCS exhibiting different effects by reserve class. These results will help to describe Reserve Force Veterans that may require more mental health assistance. LAY SUMMARY The objective of this research was to explore the association between demographic and service characteristics and mental health in Canadian Veterans of the Reserve Force. The Reserve Force Class C model showed that marital status, age, chronic pain, depression, anxiety, posttraumatic stress disorder (PTSD), and type of release were associated with mental health. The Reserve Force Class A/B model showed that age, depression, anxiety, PTSD, and type of release were associated with mental health. These results showed that similar factors were associated with the mental health score, with different degrees of association by reserve class. These results will help to better describe Reserve Force Veterans that may require mental health assistance.