Background: The aim of the present study was to investigate the role of progesterone on the developmental competence of cumulus-oocyte complexes (COCs) and cumulus-denuded oocytes (CDOs) at germinal vesicle (GV) stage. Materials and Methods: GV oocytes of pregnant mare’s serum gonadotropin (PMSG)-primed prepubertal mice were divided into two groups: CDOs and COCs. The oocytes were cultured in TCM199 with different concentrations of progesterone (10, 38, 50 and 100 μM) and without progesterone (controls). The number of oocytes at the GV, germinal vesicle breakdown (GVBD) and metaphase II (MII) stages were counted. In vitro fertilization (IVF) of MII oocytes and their development to the blastocyst stage were evaluated. Results: Significantly different MII rates were observed between the COCs (85%) and CDOs (68%) control groups. The MII rates of 83%, 48%, 14% and 0% for COCs and 65%, 53%, 20% and 0% for CDOs were obtained in TCM199 that contained 10, 38, 50 and 100μM progesterone concentrations, respectively. These MII rates were lower (p<0.05) in both COCs and CDOs as compared to their respective control groups, except for 10 μM. The fertilization and blastocyst rates of COCs (83% and 35%, respectively) were higher (p <0.05) than those of the CDOs (51% and 5%, respectively) control groups. The fertilization and blastocyst rates in the presence of 10 μM (81% and 36%, respectively) and 38 μM (85% and 30%, respectively) progesterone in COCs and CDOs (52% and 4% for 10 μM; 56% and 4% for 38 μM) were similar to their respective control groups. Conclusion: Adding progesterone to the medium could not improve maturation of mouse GV oocytes and their development to the blastocyst stage.