Objective To explore the inhibitory effect and related mechanism of paeoniflorin on proliferation of hypertrophic scar (HS) fibroblasts. Methods HS fibroblasts were cultured with 0 (control), 200, 400, 800 μmol/L of paeoniflorin for 24, 48, and 72 h. Cell viability was detected by MTT assay. Cell apoptosis was detected using Hoechst staining. Cell cycle was measured by flow cytometry. The levels of type I collagen (COL I) and type Ⅲ collagen (COL Ⅲ) were detected by enzyme linked immunosorbent assay (ELISA). The expressions of transforming growth factor-β (TGF-β)/Smad signaling pathway related proteins, as well as matrix metalloproteinase 1 (MMP1) and MMP13 were detected by Western blot. Results 200, 400, 800 μmol/L of paeoniflorin reduced the cell viability of HS fibroblasts significantly (P< 0.01), with the nuclei turning pale and shrunken, and caused cell cycle arrest at G1 phase (P< 0.01). Moreover, the levels of COL I and COL Ⅲ in the cells were decreased significantly (P< 0.01), and the expressions of MMP1, MMP13, TGF-β1, p-Smad2 and p-Smad3 were down-regulated significantly (P< 0.01). Conclusions Paeoniflorin can obviously inhibit the proliferation and collagen synthesis of hypertrophic scar fibroblasts, probably through inhibition of the TGF-β1/Smad signaling pathway.