Chronic disease interventions for women have been understudied in the workplace domain. Understanding the role of cognitions in individual behaviour can help motivate change and suggest directions for achieving improvements in health. The purpose of this study was to identify psychosocial constructs and social-cognitive theories [e.g. Transtheoretical model (TTM), Theory of Planned Behaviour (TPB), Protection Motivation Theory (PMT) and Social Cognitive Theory (SCT)] that are most salient for explaining physical activity behaviour among employed women (n = 1183). Demographic information, and social-cognitive measures related to physical activity, intention and behaviours (e.g. stage of change, energy expenditure) were assessed. A series of multiple regression analyses predicting intention, energy expenditure and stage of change were conducted separately for: (1) women with young children (n = 302), and (2) women without young children (n = 881) for each of the respective social-cognitive theories. Although taken as a whole the results were relatively similar between the two sub-groups of women for each of the socio-cognitive theories examined in this study, differences were observed in the relative contributions of the theoretical constructs between the two sub-groups. Results also indicate that self-efficacy and intention were the strongest predictors of behaviour among both women with and without young children. The explained variances (R(2)) for the theories examined in this study for different sub-groups ranged from 16 to 60%, generally reflecting what has been reported in other studies within the physical activity domain. The results of this study could be useful in guiding future research and in designing physical activity intervention programs for these specific population groups. Integrating approaches of individual lifestyle change while addressing issues related to creating supportive environments for women in various life stages is a suggested strategy for future work in this area.