The authors in this cross-sectional study examined mental health and family environmental factors related to a sedentary lifestyle, including lack of leisure-time physical activity and high levels of television viewing, among low-income mothers/female guardians of preschool-aged children. A self-administered questionnaire was completed by 131 mothers in 2010. Primary outcome measures included television viewing time (minutes/day) and leisure-time physical activity (<150 versus ≥150 minutes per week). Independent variables included depressive symptoms, perceived stress, and family functioning. Demographic factors (age, marriage, work status, education, number of children in the household, and race/ethnicity) were examined as potential covariates. Participating women watched television on average 186.1 minutes/day (i.e., >3 hours). Additionally, 36% of women engaged in less than the recommended 150-minute leisure-time physical activity per week. Hierarchical multiple regression analyses indicated that greater depressive symptoms (B = 76.4, p < 0.01) and lower family functioning (B = 33.0, p < 0.05) were independently related to greater television viewing when controlling for other variables. No independent factors were identified for lack of leisure-time physical activity when controlling for other covariates. Findings suggest that health promotion efforts to promote an active lifestyle among low-income women with young children should address mental health and family functioning factors, especially depressive symptoms.