miR-152, as a tumor suppressor, has been reported to be downregulated in a number of cancer cell lines and tumor tissues, including breast cancer. This study aimed to investigate the role of miR-152 in human breast cancer and its underlying mechanisms. Human breast cancer cell line HCC1806 was transfected with hsa-miR-152-3p mimic, inhibitor, or scrambled negative controls. The efficiency of miR-152-3p transfection was evaluated by quantitative real-time PCR, and the effects on cell viability and apoptosis as well as on the PI3K/AKT signaling pathway were investigated by MTT assay, flow cytometry, and Western blot analysis, respectively. The binding effect of miR-152-3p on PIK3CA 3'-UTR was also investigated. The results suggested that miR-152-3p mimic transfection inhibited cell viability while inducing apoptosis of HCC1806 cells. Furthermore, miR-152-3p negatively regulated PIK3CA expression via binding to the 3'-UTR of PIK3CA and decreased the phosphorylation levels of AKT (Ser473) and RPS6 (Ser235/236) in HCC1806 cells. miR-152-3p inhibitor transfection showed the opposite effects. In conclusion, miR-152-3p might serve as a tumor suppressor in human breast cancer cells via negatively regulating PIK3CA expression to inhibit the activation of AKT and RPS6, leading to suppression of HCC1806 cell proliferation.