The BRAF V600E somatic mutation is recognized as an oncogenic driver of many human cancers involving the MAPK/ERK pathway. Colorectal and lung cancers associated with the BRAF V600E mutation often demonstrated mucinous morphology. This study hypothesized that the BRAF V600E mutation may be associated with mucinous morphology in endometrial cancer and aimed to investigate its prevalence in mucinous (endometrial) carcinoma (MC) and endometrioid adenocarcinoma with significant mucinous differentiations (ECMD) (>10% neoplastic cells). Twenty-eight cases of endometrial cancer were selected, including 17 (60.7%) cases of MC or ECMD. All patients were Caucasian with age ranging from 50 to 87 years old (median 65). Genomic DNA was extracted from formalin-fixed paraffin-embedded tumor tissue and subjected to both real-time mutant allele-specific amplification polymerase chain reaction (PCR) and PCR amplification, followed by direct sequencing. Three (3/28, 10.7%) BRAF V600E mutations were detected by real-time mutant allele-specific amplification PCR and confirmed by direct sequencing. Two of 3 cases positive for BRAF V600E mutation were ECMDs with "surface epithelial changes." KRAS mutations were found in 9 cases (32.1%), none with BRAF mutation. This is the first report of BRAF V600E mutation in endometrial cancer, indicating that it may contribute to tumorigenesis of endometrial cancer, although at a low frequency compared with KRAS mutations.