Graphene quantum dots (GQDs) have received much attention for their biomedical applications, such as bioimaging and drug delivery. Additionally, they have antioxidant and anti-inflammatory properties. We used GQDs to treat renal fibrosis and confirmed their ability to protect renal cells from excessive oxidative stress in vitro and in vivo. Tubulointerstitial fibrosis was induced by unilateral ureteral obstruction (UUO) in 7- to 8-week-old male C57BL/6 mice. GQDs were administered by intravenous injection to mimic clinical treatment. The levels of oxidative stress, ROS production, apoptosis and proinflammatory cytokines and the activity of the TGFβ1/Smad pathway were evaluated after treatment with GQDs. In vitro, rhTGF-β1 was used to induce fibrosis in primary kidney tubule epithelial cells. GQDs alleviated fibrosis and morphological changes after UUO induction. At the mRNA and protein levels, GQDs significantly reduced the expression of fibrotic markers and proinflammatory cytokines, decreased ROS production and TGF-β1 expression, and affected Smad-dependent signaling pathways. In vitro, GQDs inhibited rhTGF-β1-induced epithelial-to-mesenchymal transition in primary kidney tubule epithelial cells and reduced apoptosis and ROS accumulation. This study revealed the role of GQDs in kidney fibrosis: GQDs effectively attenuated major fibrogenesis events by inhibiting ROS accumulation and the vicious cycle of the ROS and TGF-β1/Smad signaling pathways, as well as alleviating cell apoptosis and inflammation. Thus, GQDs may be a therapeutic option for chronic kidney disease progression.