Aims: To evaluate the effects of hyperlipidic diet on the mouse prostate and also investigate if physical exercise is able to restore such effects. Methodology: Adult male Swiss mice were fed with a balanced (ND) or hyperlipidic diet (45% saturated fat, HD) for 16 weeks. Half were submitted to a sedentary (NDS and HDS) or exercise routine (swimming- NDE and HDE) for 8 weeks. Then, the prostate was analyzed by immunoreactions (proliferating cell nuclear antigen- PCNA, androgen receptor- AR, and estrogen receptor-ERβ), western blotting (ERK 1/2), and caspase-3 activity. Results: We found that saturated fat uptake promoted 16% weight gain, increased fat-mass and hyperglycaemia, as well as reduced testosterone levels. In addition, HD atrophied prostate secretory epithelium and stimulated cell proliferation through higher expression of AR and activation of ERK signaling. Additionally, saturated fat reduced prostatic ERβ content. Physical exercise per se promoted an anabolic effect by increasing testosterone and stimulating cell proliferation in the prostate of sedentary animals. Finally, exercise was able to restore the proliferative signals caused by the hyperlipidic diet on prostate. Conclusion: We suggest that the combination of hyperlipidic diet and sedentary lifestyle could negatively affected some prostate stimulating pathways that could trigger proliferative diseases in mice and physical exercise may be an interesting strategy to reverse such effects.