Background Triple negative breast cancer (TNBC) is the most aggressive subtype with the worst prognosis. The role of profilin 2(PFN2) in TNBC is very controversial. The current study is to explore the role of PFN2 in TNBC. Methods PFN2 expression in TNBC and normal breast tissues were evaluated by immunohistochemical analysis. The association between PFN2 expression and prognosis in TNBC patients was analyzed from the TCGA database. A cell counting kit-8 (CCK8) assay was employed to investigate the effects of PFN2 in TNBC cell proliferations. The migration and invasion capability of TNBC cells was evaluated by transwell assays. Western blot was performed to assess the related protein expression of TGF-beta/Smad signaling and epithelial to mesenchymal transition. Finally, TNBC xenografts were established to determine the tumorigenicity in vivo using female Nod/Scid mice. Results PFN2 is upregulated in TNBC and the higher expression was associated with worse survival. CCK8 assays and Transwell assays demonstrated that PFN2 promoted the proliferation, migration and invasion of TNBC cells. Smad2 and Smad3 were upregulated in PFN2 overexpressing TNBC cells, which further induced the process of epithelial-to-mesenchymal transition. Similarly, the overexpressing PFN2 TNBC cells exhibited stronger tumorigenicity in vivo. Conclusions Higher PFN2 expression is associated with a worse 10-year overall survival and relapse-free survival in breast cancer patients, as well as worse 10-year relapse-free survival in TNBC patients. PFN2 promotes the proliferation, migration and invasion of TNBC cells by regulating epithelial-to-mesenchymal transition.