INTRODUCTION: The ketogenic diet (KD) is a very‑low‑carbohydrate, high‑fat and adequate protein nutritional approach that induces metabolic shift to the use of ketone bodies instead of glucose as a main energy source. For decades, the KD has been employed to manage drug-resistant epilepsy, but recently it is increasingly considered as an alternative or add-on therapy in many other disorders. The positive effect of the KD on social behavior has been recently reported in rodent models of autism spectrum disorder (ASD) and wild type early adult male rats. AIM(S): Given, however, the influence of ketone bodies on many humoral parameters including testosterone, we decided to look closer at the sexual interactions of male rats subjected to the KD. METHOD(S): In our study, we examined behavior of males in response to female presence with concomitant analysis of ultrasonic vocalizations (USV) during sexual interactions. RESULTS: Percent of males starting to copulation significantly decreased during the second sexual session, which suggests lower sexual motivation in male rats on the KD. FINANCIAL SUPPORT: Funding: Ministry of Science and Higher Education, grant number KNW‑1‑053/N/8/I.