Hypoxia-inducible factors (HIFs) are transcription factors consisting of an oxygen-sensitive α-subunit binding to a stable β-subunit. HIFs regulate multiple signaling pathways that could contribute to fibrogenesis, supporting their potential role in hypoxia-mediated renal fibrosis. We previously reported that HIF-1 is upregulated and required for TGF-β induction of collagen in renal tubular cells. Here, we performed in vitro and in vivo studies of potential glomerular crosstalk between transforming growth factor (TGF)-β and normoxic HIF signaling. HIF-α has two major isoforms, HIF-1α and HIF-2α, with different target gene sets. In cultured human mesangial cells (HMC), TGF-β1 treatment increased both HIF-1α and HIF-2α expression in normoxia. TGF-β1 did not increase HIF-1α/2α mRNA levels nor decrease the rate of protein degradation, suggesting that it enhances HIF-1α/2α expression through translation. TGF-β receptor (ALK5) kinase activity was required for increased, TGF-β-stimulated HIF-α expression in response to TGF-β, and inhibiting PI3-kinase markedly decreased HIF-α expression. Blocking HIF-1α/2α expression using siRNA decreased basal and TGF-β1-stimulated type-I collagen expression, while overexpressing non-degradable HIF-α increased the collagen response, with HIF-2α being significantly more effective than HIF-1α. In Adriamycin (ADR)-induced mouse glomerulosclerosis, HIF-2α target genes were upregulated in sclerosing glomeruli. Taken together, our data demonstrate potential signaling interaction between TGF-β and HIFs to promote renal fibrogenesis in normoxia and suggest that the HIF-2α isoform is more important during glomerulosclerosis.