BACKGROUND: Mounting evidence shows that tumor-derived extracellular vesicles (EVs) are critical constituents in the tumor microenvironment. The composition and function of EVs often change during cancer progression. However, it remains less clear how cancer cells modulate their own EV biogenesis to promote tumor development. The release of EVs is closely linked to the endolysosome system residing within the cell. The current study aims to decipher the role of endosomal protein DENND10 in cancer development. RESULTS: Bioinformatics data mining showed that DENND10 expression is significantly associated with poor prognosis in multiple cancer types and up-regulated in metastatic breast cancer cell lines. DENND10 knockout (DENND10-KO) in breast cancer cells led to defective EV biogenesis due to impaired endolysosomal trafficking. Intriguingly, DENND10-KO cells exhibited reductions in cell spreading, migration, invasion, and metastatic potential in vivo. These deficiencies in cell motility were associated with compromised cytoskeleton organization. Importantly, wild-type conditioned medium or EVs restored the migratory ability and cytoskeletal organization of DENND10-KO cells. Global proteomic profiling revealed that DENND10 depletion led to a distinct EV compositional landscape with remodeled profiles of extracellular matrix (ECM) and adhesion molecules. Consistently, exogenous application of ECM molecules rescued the spreading and migration of DENND10-KO cells. CONCLUSIONS: In summary, our study unveiled DENND10 as an intrinsic regulator of cell migration that modifies the tumor microenvironment through autocrine EV release, which could be exploited for developing targeted therapies for tumor metastasis. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12915-024-01948-4.