The objective of this study was to investigate the role of miR-148a-3p in lupus nephritis (LN) based on data from previous studies and a microRNA assay. We evaluated the miR-148a-3p expression level in LN renal tissues and blood serum to determine its clinicopathological significance and effect on glomerular cell proliferation. Then, we collected renal glomeruli from LN mice and determined the miR-148a-3p, proliferating cell nuclear antigen (PCNA), and PCNA/Thy1 expression. We performed functional analyses of miR-148a-3p in vitro and in vivo. We also investigated the target gene of miR-148a-3p in LN. The results showed that miR-148a-3p expression levels were significantly higher not only in glomeruli but also in the blood serum during LN and increased in the glomeruli of LN mice and that at the same time there was positive correlation between miR-148a-3p and PCNA expression of glomruli. Overexpression of miR-148a-3p accelerated cell proliferation and PCNA expression, while a miR-148a-3p inhibitor inhibited cell proliferation via the Akt/cyclin D1 pathway. Furthermore, miR-148a-3p overexpression reduced the phosphatase and tensin homology deleted on chromosome ten (PTEN) expression level, while miR-148a-3p silencing increased its expression in high-mobility group box 1 (HMGB1)-induced mouse mesangial cells (MMCs). Luciferase assays demonstrated that miR-148a-3p could directly bind to the PTEN 3′-UTR. PTEN overexpression inhibited MMC proliferation considerably, resembling the results observed during miR-148a-3p inhibition. Reducing miR-148a-3p expression upregulated PTEN in the glomeruli and improved renal function in LN mice. Thus miR-148a-3p may promote proliferation and contribute to LN progression by targeting PTEN.