Background Mycophenolate mofetil (MM F) has been used to prevent transplant rejection for many years and has been shown to have protective effects against renal failure. The objective was to investigate the effect of MMF on monocyte Toll-like receptor 4 (TLR4) signaling in the early stages of renal ischemia/reperfusion injury (IRI) of mice. Methods Sixty BALB/C mice were randomly divided into two groups: an IRI group, in which renal IRI was induced by clamping the renal pedicles for 45 minutes, and an MMF group, in which MMF was given (40 mg.kg(-1).d(-1), intraperitoneally) from 2 days before renal IRI. The plasma creatinine level and renal tissue damage of each group mice were observed 6, 12, 24, and 48 hours after reperfusion. The concentration of plasma high-mobility group box 1 (HMGB-1) (TLR4 ligand), interleukin 6 (IL-6), nnonocyte chemoattractant protein-1 (MCP-1), and tumor necrosis factor alpha (TNF-alpha) and the expression of TLR-4 on monocytes were determined. Results The plasma creatinine concentration in the MMF group was lower compared to the IRI group (after reperfusion of 6, 12, 24, or 48 hours, P <0.05). Pathological analysis showed that the renal damage was slighter, TLR-4 expression was reduced (after reperfusion of 6, 12, 24, or 48 hours, P <0.05), and the concentration of cytokines in the plasma was lower (P <0.05) in the MMF group. No differences in the concentrations of HMGB-1 were observed (P >0.05). Conclusion Monocyte TLR4 signaling is important in the early stage of kidney IRI, but MMF can inhibit it and improve renal function.