Introduction: Bisphenol A (BPA) is a widespread compound in the plastic industry that is especially used to produce baby bottles, food packaging and metal cans. BPA, an endocrine disruptor, leads to alterations in reproductive function and therefore has been banned from the food industry. Unregulated BPA analogues, particularly Bisphenol S (BPS), have emerged and are now used in the plastic industry. Thus, this study aimed to examine the acute effects of low and environmental doses of BPS on ewe oocyte quality and developmental competence, and its mechanism of action, during in vitro maturation. Methods: Ewe cumulus-oocyte complexes underwent in vitro maturation in the presence or absence of BPS (1 nM, 10 nM, 100 nM, 1 μM or 10 μM). Oocytes were then subjected to in vitro fertilisation and development. Results:1 μM BPS induced a 12.7% decrease in the cleavage rate (p= 0.004) and a 42.6% decrease in the blastocyst rate (p= 0.017) compared to control. The blastocyst rate reduction was also observed with 10 nM BPS. Furthermore, 10 μM BPS reduced the oocyte maturation rate,and 1 μM BPS decreased cumulus cell progesterone secretion. PRand AMHgene expression were reduced in cumulus cells. BPS induced a 5-fold increase in MAPK 3/1 activation (p= 0.04). Conclusions:BPS impaired ewe oocyte developmental competence. The data suggest that BPS might not be a safe BPA analogue. Further studies are required to elucidate its detailed mechanism of action