The addition of selected growth factors to in vitro embryo culture medium improves the viability of cultured preimplantation embryos. One such beneficial growth factor is sphingosine 1-phosphate (S1P). Exogenous S1P improves oocyte maturation (Cheng et al., 2015; Jee et al., 2011) and rate of blastocyst formation (Jee et al., 2011) and decreases rates of apoptosis throughout development (Guzel et al., 2018; Roth and Hansen, 2004). The mechanism by which S1P improves development is poorly understood. The current study aims to determine the expression of the S1P1 receptor (S1P1R) in the mouse preimplantation embryo and its role in endogenous signalling pathways that may promote preimplantation embryo development. Immunofluorescence staining demonstrated that the S1P1R is expressed in both the plasma membrane and the nucleus in the early stages of preimplantation development and is predominantly within the nucleus at later stages. Within the blastocyst, the S1P1R was expressed in the trophectoderm cells as well as the hypoblast cells, but not the epiblast cells of the inner cell mass. Activation of the S1P1R by exogenous S1P in 2-cell embryos resulted in changes in S1P1R localisation when visualised via immunofluorescence. Most notably, a decrease in nuclear and cytoplasmic S1P1R staining was observed in embryos treated for at least 5 minutes. Finally, treatment of embryos with NIBR-0213, a potent and selective S1P1R antagonist, resulted in a dose-dependent decrease in the percentage of embryos that developed to the morula stage and beyond. Together, these findings support the presence and function of the S1P1R in the mouse preimplantation embryo and suggest that endogenous S1P/S1P1R signalling is necessary for preimplantation embryo development, though the exact signalling pathways remain to be elucidated.