Exosomes are key mediators of intercellular communication and play a role in the pathogenesis and progression of cancer. Exosomes in circulating body fluids serve as molecular markers for cancer diagnosis. This study aimed to investigate the role of exosomal microRNA (miR)-1910-3p in breast cancer and determine its clinical diagnostic value. MiR-1910-3p promoted proliferation and migration of breast cancer cells in vitro and in vivo. In vitro, exosomes enriched in miR-1910-3p transferred miR-1910-3p to mammary epithelial cells and breast cancer cells, promoting proliferation and migration, inhibiting apoptosis, and inducing autophagy. In vivo, exosomes enriched in miR-1910-3p promoted the proliferation and migration of breast cancer cells. MiR-1910-3p downregulated myotubularin-related protein 3, activated the NF-κB and wnt/β-catenin signaling pathway, and promoted breast cancer progression. Serum miR-1910-3p in exosomes was an effective diagnostic marker that improved the sensitivity of breast cancer diagnosis when used in combination with the traditional tumor marker CA153. In conclusion, breast cancer cell-derived exosomes promoted the growth, metastasis, and autophagy of breast cancer cells by transferring miR-1910-3p. MiR-1910-3p in serum exosomes may serve as a novel molecular marker for breast cancer diagnosis. •Exosome miR-1910-3p promoted proliferation and migration of breast cancer cells in vitro and in vivo.•Exosomes transferred miR-1910-3p, promoting proliferation and migration, and inducing autophagy in breast cancer.•MiR-1910-3p downregulated MTMR3, activated the NF-κB signaling pathway, and promoted breast cancer progression.•Serum miR-1910-3p in exosomes was an effective diagnostic marker that improved the sensitivity of breast cancer diagnosis.