There is ample evidence that a key contributor to healthy aging is social participation; thus, identifying its determinants can help to improve it. The current study aimed at assessing the relationship between social support and general self-efficacy with social participation. This cross-sectional study was conducted on 456 (male: 237, female: 219) older adults, aged 60-74 years, who were the member of community centers in Tehran, Iran, in 2016. The multi-stage cluster sampling method was employed to select the participants. Primarily, Tehran was divided into five areas (i e, North, South, East, West, and Center). Then, two community centers were randomly selected from each area. Participants with the ability to perform their daily activities independently were enrolled in the study. Participants responded to four self-report questionnaires: socio-demographic, social participation, social support, and general self-efficacy. The majority of the participants were within the age range of 62–68 years with the maximum proportion of social participation (mean ± standard deviation (SD): 37.69 ± 8.34). Findings of the current study indicated that gender, education level, reading books, newspapers, or magazines (p <0.001), living area, living arrangement, and occupational status (p<0.05) were associated with social participation. Multiple linear regression adjusted for living area, sex, and educational level showed that self-efficacy (β= .08; p<.001) and social support (β= .64; p<.001) predicted social participation. Findings showed the importance of social support and self-efficacy in social participation. Also enhancing the literacy of seniors should be given priority.