Considering the negative side effects of chemical drugs, there is a great need for effective alternative treatment strategies to manage cyclical mastalgia. Therefore, this study aimed at comparing the effects of flaxseed diet and omega-3 fatty acids supplement on treatment of cyclical mastalgia. In this study, 61, 60, and 60 women, respectively, received flaxseed as bread, omega-3 fatty acids as pearl, and wheat bread as their diet for two menstrual cycles. At the baseline cycle and end of both interventional cycles, intensity of mastalgia was measured using visual analogue scale. Analysis of covariance showed a significant difference among the three groups regarding the mean intensity of cyclical mastalgia in the first and second cycles of the interventions (P < 0.001). Also, repeated measures analysis of covariance with adjustment of two variables of age and mastalgia intensity of the baseline cycle demonstrated that flaxseed bread was more effective compared to omega-3 and wheat bread (P < 0.001). The results of this study demonstrated that flaxseed bread diet was an effective approach in decreasing cyclical mastalgia and could be prescribed to women as a simple treatment with few complications.