This study tests the associations of self-efficacy, outcome expectancies, perceived barriers, self-regulatory behaviors and social support with physical activity. Data from 116 married community-dwelling middle-aged and young-old couples (M = 58.86 years, SD = 7.16, range = 50 to 75) were collected via mail-in survey. The model indicated that self-efficacy was directly and indirectly related to physical activity through outcome expectancies, perceived barriers and self-regulatory behaviors. The results clarify the associations among the social cognitive constructs and physical activity, and suggest that interventions targeting multiple social cognitive constructs could increase the activity levels of middle-aged and young-old adults.