There has recently been constant effort to evaluate therapies that may have a positive effect on bone regeneration. However, there are few studies in the literature on the effects of low-level laser therapy (LLLT) involving tissues treated with anabolic steroids. The present study evaluated the effects of LLLT (AsGaAl 780 nm, 3 J/cm(2), 10 mW, beam spot of 0.04 cm(2), total energy 0.12 J) on the proliferation, adhesion, and differentiation of osteoblasts cultured in the presence of nandrolone decanoate (ND). The MTT method was employed to evaluate cell proliferation and adhesion. Cell differentiation was evaluated by measuring alkaline phosphatase activity. There was a significant decrease in cell proliferation in the irradiated group treated with 50 μM ND when compared to the control group, after 48 h. After 72 h, cell proliferation was significantly greater in the control group than in the irradiated groups treated with the steroid at concentrations of 10, 25, and 50 μM. With regard to cell differentiation, alkaline phosphatase activity was significantly higher in the irradiated group treated with 50 μM ND than in the control group, irradiated non-treated group, and irradiated group treated with 25 μM ND. After 60 min of plating, the irradiated non-treated group and irradiated groups treated with the steroid at concentrations of 5, 10, and 25 μM exhibited a significant increase in cell adhesion compared to the control group. LLLT in combination with a high concentration of steroid inhibited cell proliferation, possibly by inducing cell differentiation, while irradiation combined with lower concentrations of the steroid induced an increase in cell adhesion.