Background: Sedentary lifestyle is known to be a potential risk factor for chronic diseases. Given the vital role that physical activity plays in the prevention of chronic diseases in middle-aged women, this study was conducted to develop the intention for performing physical activity among middle-aged women based on the motivational phase constructs of the health action process approach model. Methods: This quasi-experimental study was conducted on 160 middle-aged women of Jovein, Iran, in 2016. Subjects were randomly selected using a multi-stage sampling method, and assigned to the control (n = 80) and intervention (n = 80) groups. The motivational phase constructs of the health action process approach and physical activity intention were measured at three stages; before the intervention, immediately following the intervention, and 1 month after the intervention. Data were analyzed using SPSS 17.0 software with the Chi-square test, Pearson's correlation, ANOVA, and Friedman tests. Results: One month after the intervention, the number of women with an intention to engage in physical activity was significantly higher in the intervention group (n = 56, 73.6%) compared to the control group (n = 23, 29.8%) (P < 0.001). Immediately following the intervention and 1 month after the intervention, all motivational phase constructs were significantly increased in the intervention group compared to before the intervention (P < 0.001). However, no significant change was observed in the control group. Moreover, immediately following the intervention and 1 month after the intervention, all motivational phase constructs were significantly increased in the intervention group compared to the control group (P < 0.001). Conclusion: The results demonstrate the effectiveness of empowerment program based on the motivational phase constructs of the health action process approach on developing the intention for performing physical activity among middle-aged women. [ABSTRACT FROM AUTHOR]