Uterine cancer is a prevalent gynecological malignancy globally. Endometrial carcinosarcomas constitute a rare and aggressive subtype of uterine malignancy. In recent years, immunotherapy has emerged as a treatment option after the failure of platinum-based chemotherapy. This case series explores the use of pembrolizumab and lenvatinib in treating endometrial carcinosarcoma. This retrospective case series was conducted at a single tertiary care center in northern New Jersey, United States, and included patients seen between 2019 and 2023 who had confirmed uterine carcinosarcoma treated with pembrolizumab and lenavatinib. Patient demographics, oncologic characteristics, and details of immunotherapy were extracted from electronic medical records (Epic). Statistical analysis included survival analysis for progressionfree survival (PFS) and overall survival (OS). A total of eight patients with endometrial carcinosarcoma, microsatellite stable, were treated with pembrolizumab plus lenvatinib and included in the case series. All patients received cytoreductive surgery and chemotherapy with carboplatin plus paclitaxel. The median follow-up duration with the oncologist was 5.6 months (IQR (Interquartile range): 3.5, 9.0). OS ranged from 0.4 to 19.3 months. One patient was excluded from the OS analysis due to a loss of follow-up. The median PFS was 3.6 months (IQR: 1.8, 4.4). This case series provides valuable insight into applying pembrolizumab and lenvatinib as a second-line treatment for endometrial carcinosarcoma after the failure of platinum-based chemotherapy. The observed improvements in PFS and OS, coupled with manageable side effects, highlight the potential efficacy of this treatment.