The transforming growth factor-beta (TGF-β) signaling pathway plays critical roles in the development of various diseases. The current study investigated whether TGF-β was involved in the pathogenesis of osteosarcoma from the genetic polymorphism perspective and serum level perspective. We first examined two TGF-β1 polymorphisms, rs1800469C/T and rs1800470T/C, in 202 osteosarcoma patients and 216 healthy controls. Data revealed that the prevalence of rs1800470TT genotype and T allele was significantly elevated in patients than in controls (odds ratio [OR]=2.28, 95% confidence interval [CI]: 1.30-3.98, p<0.001, and OR=1.49, 95% CI: 1.14-1.96, p<0.001). Function analyses showed that healthy controls carrying rs1800470TT genotype had a significantly higher serum level of TGF-β than those carrying the rs1800470CC genotype (191.1±15.7 pg/mL vs. 129.4±10.9 pg/mL, p=0.003). We then compared the serum level of TGF-β between osteosarcoma patients and healthy controls. Results demonstrated a significantly increased serum level of TGF-β in patients than in controls. Further analyses identified that patients with metastasis had augmented levels of serum TGF-β than those without metastasis. These data indicate that TGF-β may be closely involved in the pathogenesis of osteosarcoma.