Epithelial ovarian cancer (EOC) is classified into five major histotypes: high-grade serous (HGSOC), low-grade serous (LGSOC), clear cell (CCOC), endometrioid (ENOC), and mucinous (MOC). However, the landscape of molecular and immunological alterations in these histotypes, especially LGSOC, CCOC, ENOC, and MOC, is largely uncharacterized. We collected 101 treatment-naive EOC patients. The resected tumor tissues and paired preoperative peripheral blood samples were collected and subjected to target sequencing of 1021 cancer-associated genes and T cell repertoire sequencing. Distinct characteristics of mutations were identified among the five histotypes. Furthermore, tumor mutation burden (TMB) was found to be higher in CCOC and ENOC, but lower in LGSOC and HGSOC. Alterations associated with DNA damage repair (DDR) pathways and homologous recombination deficiencies (HRD) were prevalent in five histotypes. CCOC demonstrated increased level of T cell clonality compared with HSGOC. Interestingly, the proportion of the 100 most common T cell clones was associated with TMB and tumor neoantigen burden in CCOC, highlighting more sensitive anti-tumor responses in this histotype, which was also evidenced by the enhanced convergent recombination of T cell clones. These findings shed light on the molecular traits of genomic alteration and T cell repertoire in the five major EOC histotypes and may help optimize clinical management of EOC with different histotypes.