The objective is to investigate the effect of high mobility group box-1 (HMGB1) on lipid deposition in γ-interferon (IFN-γ)-stimulated mouse mesangial cell line (MMC) and to determine whether the Janus kinase 2 and signal transducer and activator of transcription 1 (JAK2/STAT1) signaling pathway plays an important role in this process. We employed a control group, an IFN-γ stimulation group, and an IFN-γ + AG490 (JAK2 inhibitor) group. RNA interference aimed at sterol regulatory element-binding protein-1 (SREBP-1) or HMGB1 was used to investigate the effect of these proteins on IFN-γ-induced lipid deposition. Western blotting was used to detect phospho (p)-JAK2, JAK2, p-STAT1, STAT1, SREBP-1, fatty acid synthase (FAS), and HMGB1 protein expression. RT-PCR was used to detect SREBP-1, FAS, and HMGB1 mRNA. Oil Red O staining and the triglyceride assay were used to detect lipid deposition and triglyceride content. Results were as follows: 1) IFN-γ increased MMC cell lipid deposition, triglyceride content, and p-JAK2, p-STAT1, SREBP-1, and FAS expression; 2) SREBP-1 inhibition prevented FAS upregulation and attenuated IFN-γ-induced MMC cell lipid deposition and triglyceride content; 3) HMGB1 upregulated SREBP-1 and FAS mRNA and protein levels, which increased lipid deposition in MMC cells. Small interfering RNA-mediated inhibition of HMGB1 decreased SREBP-1 and FAS expression and lipid accumulation; 4) AG490 decreased upregulation of HMGB1 and p-JAK2/p-STAT1, as well as IFN-γ-induced lipogenesis. In conclusion, the JAK2/STAT1 pathway mediates IFN-γ-induced lipogenesis in MMC cells through regulation of HMGB1/SREBP-1/FAS.