Background: Colorectal cancer (CRC) is a major cause of mortality and morbidity. A study proved that brexpiprazole, as a novel dopamine receptor partial agonist, can also prevent CRC cell proliferation. Therefore, clarifying the molecular mechanism of brexpiprazole is vital to developing a novel therapeutic strategy for CRC. Methods: The effect of brexpiprazole on human colorectal cancer cell proliferation was measured with Cell Counting Kit-8 (CCK-8) kits. Cell migration capability was measured using wound healing and transwell. Cell apoptosis was evaluated with a flow cytometer. Western blots and immunohistochemical staining were used to evaluate protein expression. The effects observed in vitro were also confirmed in xenograft models. Results: Brexpiprazole remarkably inhibited the proliferation, suppressed the migration ability, and induced apoptosis of colorectal cancer cells. Mechanism study showed that brexpiprazole exerted these effects by inhibiting the EGFR pathway. Brexpiprazole enhanced HCT116 cells’ sensitivity to cetuximab, and a combination of brexpiprazole and cetuximab inhibited xenograft tumor growth in vivo. Conclusions: Our finding suggested that brexpiprazole inhibits proliferation, promotes apoptosis, and enhances CRC cells’ sensitivity to cetuximab by regulating the EGFR pathway and it might be an efficacious treatment strategy for CRC.