Background: Older people are vulnerable groups whose physical activity (PA) guarantees their health. Considering the low level of PA and the role of various factors, this study was designed to investigate the level of PA and its determinants using the socio-ecological approach.Material and methods: In 2016, a random sample of 340 older people in urban areas of the Maku county, West Azerbaijan province, Iran, were recruited to complete PASE (Physical Activity Scale for the Elderly) and a socioecological approach-based questionnaire. Structural equation modeling (SEM) was conducted by Stata. Results:The mean PA in our study was very low (94.02 ±3.41), and 50% of the participants had insufficient PA. The socio-ecological approach suggested that family support of the social level strongly affects PA (β = 2.79). Moreover, the psychological level had direct effects on PA (β = 2.79). The environmental level had effects on PA in a reverse direct as well as an indirect way (β = -2.09). Conclusions:The socio-ecological approach was found to be helpful in categorizing the determinant factors of PA among Iranian older people. Future research should focus on designing social support and self-efficacy interventional programs with a multilevel approach aiming at PA promotion among elder.