Bromodomain 4 (BRD4), a member of the bromodomain and extraterminal protein family, plays an important role in the physiological activities of normal cells and tumor cells by regulating gene transcription and cell cycle. As a transcriptional and epigenetic regulator, BRD4 gene overexpression, rearrangement and mutation are often associated with a variety of diseases, especially malignant tumors. Here, the authors review and analyze the function of BRD4 and its inhibitors in transcriptional regulation and their interaction with tumor cells, hoping to provide new ideas for relevant clinical treatment.