Introduction Bisphenols, as endocrine disruptors, may cause a wide range of health problems in humans, but so far, not all of them have been confirmed in animals, including pigs. Since animals are also exposed to bisphenols, we hypothesised that these substances may have an effect on uterine contractility in pigs. Therefore, the aim of the study was to investigate the effect of the most-used bisphenol, bisphenol A (BPA), and a selected analogue, bisphenol F (BPF), on the contractile activity of the pig uterus. Material and Methods The investigation utilised smooth muscles from immature pigs (n = 6), cyclic pigs on days 12–14 of the oestrous cycle (n = 6) or early pregnant pigs on days 12–16 of pregnancy (n = 6). Strips of the myometrium were exposed to BPA and BPF at concentrations of 10−13–10−1 M. Smooth muscle contractility was determined with equipment for measuring isometric contractions. Results BPA caused a significant decrease in contraction amplitude, and frequency and in myometrial tension in all groups examined. BPF caused a decrease in the amplitude and frequency of contractions in all groups and in myometrial tension in the early pregnant group. Conclusion The obtained results indicate that both BPA and BPF relaxed the porcine myometrium, but these changes, especially in the amplitude and frequency of contractions, were more evident after BPF treatment. The extent of relaxation is dependent on the physiological status of the animals.