Objective To investigate the effect of progranulin (PGRN) on the invasion and migration of mouse breast cancer 4T1 cells and its mechanism. Methods After treated with PGRN (1 μg/mL) for 24 hours, the invasion ability of breast cancer 4T1 cells was detected by TranswellTM invasion assay, the migration ability was detected by scratch test, and the epithelial cadherin (E-cadherin), vimentin mRNA expression was detected by real-time fluorescent quantitative PCR. Western blot assay was used to detect the expression of E-cadherin, vimentin, extracellular signal-regulated kinase 1/2 (ERK1/2) and phosphorylated ERK1/2 (p-ERK1/2). After treated with 1 μg/mL PGRN and ERK1/2 signaling pathway inhibitor U0126 (10 μmol/L) simultaneously, the migration and invasion ability of 4T1 cells and the changes in the expression of E-cadherin, vimentin and p-ERK proteins were detected again. Results After treated with PGRN, the migration and invasion capabilities of breast cancer 4T1 cells were significantly enhanced; E-cadherin expression decreased; vimentin and p-ERK1/2 expression increased. After treated with ERK1/2 signaling pathway inhibitor, the ability of PGRN to promote breast cancer 4T1 cell migration, invasion and epithelial-mesenchymal transition (EMT) was significantly inhibited. Conclusion PGRN can promote the migration and invasion of breast cancer 4T1 cells by promoting EMT and activating the ERK1/2 pathway.