Histologically distinct tumors that coexist in an organ without any histological admixture at their interface are denominated collision tumors. We report 3 cases of colliding mature cystic teratoma with mucinous cystadenoma and a case of mature cystic teratoma colliding with benign Brenner tumor in the ovary. We also provide a literature review based on 35 previously published ovarian collision cases. Ovarian tumors from all classes, benign, borderline and malignant lesions may collide. Both our case series and the literature review indicate that ovarian tumor collisions tend to be clinically and ultrasonographically/radiologically unrecognized. The awareness among surgeons, radiologists and pathologists of this rare phenomenon and histological recognition are crucial in order to offer adequate treatment to patients. There is a need to identify novel and more specific imaging clues pointing towards collision tumors in the ovary.