The malignant transformation of mature cystic teratomas during pregnancy is a rare occurrence in medical literature. In this case report, we present a remarkable instance of mucinous intestinal adenocarcinoma arising from a mature ovarian cystic teratoma diagnosed during pregnancy. This is among the few reports detailing the effective use of the FOLFOX 6 chemotherapy regimen for treating this type of intestinal cancer. Furthermore, we emphasize the immunohistochemical results that confirm the colorectal histological origin.