Collision tumor means the coexistence of two adjacent, but histologically distinct tumors without histologic admixture in the same tissue and is rare incidence involving ovary. Because of their incidence of occurrence, benign cystic teratomas often occur coincidentally with other abnormalities of the ovary. Most common histologic combination of collision tumor in the ovary is coexistence of teratoma with mucinous tumors. But its association with serous tumor has been noted rare and incidence is unknown. We have experienced a case laparoscopic treatment of a huge serous cystadenoma combined with ovarian benign cystic teratoma in right ovary, and report it with a brief review of literature.