A rare case of primary ovarian pregnancy is reported. The multiple diagnostic problems and the unclear symptomatology delayed the time of the definitive diagnosis more than seventy five days. All the histological criteria for the classification of an ovarian pregnancy are faced in this case. The finding of a well conserved gestational sac and embryo inside the ovarian tissue makes this case even more rare and interesting. When there is a suspicion of ectopic or ovarian pregnancy the Authors strongly suggest an early laparoscopy to make a reliable and precocious diagnosis, avoid the risk of the hemoperitoneum, perform a conservative therapy and preserve the ovarian function with the patient's reproductive potential.