Introduction Precise cytological diagnosis of pelvic high‐grade serous carcinoma (HGSC) in ascites is important for tumour staging, therapeutic decision‐making and prognostic evaluation. However, it can often be difficult to distinguish metastatic HGSC cells from reactive mesothelial cells based on morphology alone. Immunocytochemical analysis of ascites cell blocks has been used to obtain accurate diagnosis and provide a reliable basis for treatment decisions in the clinic. This study was performed to determine whether a panel of antibodies is necessary to achieve high specificity and sensitivity for the identification of HGSC cells. Methods Ascites samples from 70 cases (70/253, 27.7%) of histologically confirmed HGSC were postoperatively collected from 2012 to 2015 and were immunocytochemically analysed. Results The sensitivity and specificity of Ber‐EP4 (a marker of HGSC) for detecting HGSC was 85.7% and 82.1%, respectively, whereas the sensitivity and specificity of HBME‐1 for identifying mesothelial cells was 100% and 68.3%, respectively. To improve the rate of detection further of HGSC, 29 cases of ascites were also stained for E‐cadherin (a marker of HGSC) and calretinin (a marker of mesothelial cells). The combination of Ber‐EP4 and E‐cadherin as markers of adenocarcinoma cells increased the sensitivity and specificity for HGSC detection to 100% and 88.9%, respectively. Meanwhile, the sensitivity and specificity for mesothelial cell identification increased to 100% and 90%, respectively, when HBME‐1 and calretinin were combined. Conclusion This panel of complementary biomarkers is valuable and ideal for the differential diagnosis of HGSC based on ascites cytology.