Background: The aim of this study was to investigate cytological features of Brenner tumors according to tumor grade using imprint cytology. Case: Between 2004 and 2015, intraoperative imprint cytology was performed on 8 patients with Brenner tumors suspected to be malignant neoplasmas on gross examination because of their large size and solid part. These consisted of 1 benign, 3 borderline, and 4 malignant tumors. In patients with benign and borderline tumors, naked nucleus-like stromal cells and tumor cells in a sheet-like arrangement were observed against a clear background. The nuclei were round to oval-shaped with finely granular chromatin patterns and small nucleoli. Papillary cell clusters and high nucleus-to-cytoplasm ratios were only observed in 1 borderline case. In cases with malignancy, the background was necrotic. The tumor cells occurred in large papillary clusters. The nuclei showed a high degree of nuclear atypia. Nuclear grooves were present in 6 of our 8 cases and they were scant in the malignant cases. Conclusion: Imprint cytology of Brenner tumors provided no characteristic findings to enable a definitive distinction of benign versus borderline tumors, but it enabled discrimination between malignant and other tumors. Imprint cytology can facilitate intraoperative diagnosis and aid in selecting the appropriate surgical procedure.