MicroRNAs (miRNAs) are small non-coding RNAs, 8-23 nucleotides in length, which regulate gene expression at the post-transcriptional level. The present study was performed to analyze the association between microRNA‑21 and cisplatin resistance in epithelial ovarian cancer (EOC) SKOV3 and SKOV3/DDP cells. In this experiment, the resistance of SKOV3 and SKOV3/DDP cells to cisplatin was evaluated using the MTT assay. Reverse transcription‑quantitative polymerase chain reaction analysis was used to assess miRNA‑21 levels and phosphatase and tensin homolog (PTEN) mRNA levels. Western blotting was used to assess PTEN protein levels. miRNA‑21 mimics or inhibitors were transfected into SKOV3 and SKOV3/DDP cells. Prior to transfection, higher expression levels of miRNA‑21 were observed in SKOV3/DDP cells compared with SKOV3 cells. Following transfection with miRNA‑21 mimics, SKOV3 cells demonstrated increased sensitivity to cisplatin compared with negative control cells. Following transfection with the miRNA‑21 inhibitor, SKOV3/DDP cells demonstrated decreased sensitivity to cisplatin compared with negative control cells. Furthermore, PTEN mRNA expression levels in SKOV3 cells transfected with miRNA‑21 mimics was significantly lower compared with negative control cells. These results suggested that miRNA‑21 may regulate cisplatin resistance by negatively targeting PTEN in EOC.