Multiple myeloma (MM) is a malignancy characterized by plasma cell hyperplasia. The majority of patients with MM suffer from mortality due to tumor recurrence and metastasis, which has become an emerging clinical problem. Transforming growth factor β1 (TGFβ1) has been implicated in tumor metastasis; however, its role in RPMI 8226 cells remains to be elucidated. In the present study, RPMI 8226 cells were treated with various concentrations of SB431542, a TGFβ1 inhibitor, for 12, 24 and 48 h. RPMI 8226 cells were transfected with lentiviral‑TGFβ1 vectors to overexpress TGFβ1. Cell proliferation rate was subsequently determined by cell‑counting kit‑8 assay and cell invasion was assessed by Transwell assay. Expression of TGFβ1, SMAD family member 2 (Smad2) and matrix metallopeptidase 3 (MMP3) were analyzed by western blotting. The results demonstrated that cell proliferation and invasion of RPMI 8226 cells was significantly inhibited by SB431542 (P< 0.05). SB431542 was able to significantly downregulate the expression of TGFβ1, phosphorylated (p)‑Smad2 and MMP3; however, the overexpression of TGFβ1 significantly upregulated the expression of TGFβ1, p‑Smad2 and MMP3. In conclusion, SB431542 reduced cell invasion in RPMI 8226 cells, and this effect may be mediated via the TGFβ1/Smad2/MMP3 signaling pathway.