We investigated the associations among self-perceived work and life stress, trouble sleeping, physical activity and body weight among Canadian adults, and tested whether trouble sleeping and physical activity moderated the relationship between work/life stress and body weight, and whether work/life stress and physical activity moderated the relationship between trouble sleeping and body weight. Data on 13,926 Canadian adults aged 20years and older were derived from the nationally representative 2012 Canadian Community Health Survey. After adjusting for age, sex, education level, household income, marital status and job insecurity, self-perceived work and life stress and trouble sleeping were associated with a higher BMI. The associations of work and life stress with higher BMI were independent of trouble sleeping and physical activity in addition to other covariates, while that of trouble sleeping and higher BMI was independent of work and life stress. Results further indicated that trouble sleeping among inactive participants was related to a higher BMI; however, this relationship was almost null for adults who self-reported being physically active for about 8h/week. These findings suggest that work and life stress are both associated with excess weight in adults, regardless of physical activity level, while the link of trouble sleeping with BMI varies by physical activity level. Future research is necessary to determine whether reducing work and lifestress and improving sleep habits would benefit the prevention of weight gain and obesity.