This study was performed to evaluate whether glycerol supplementation and ambient temperature affects growth and blood metabolic and immunological parameters in beef cattle. Twenty Korean cattle steers with average 14.4 mo of age and 405 kg of body weight (BW) were used. Animals were divided into conventional control diet group and 2% glycerol supplementation group. Steers were allowed a concentrate diet with the amount of 1.5% of BW and a tall fescue with the amount of 0.75% of BW for 8 weeks. Experimental period 1 (P1) was 4 weeks from July 28 to August 26, and period 2 (P2) 4 weeks from August 27 to September 26. Blood was collected 4 times at July 28, August 11, August 27, and September 26. Maximum temperature-humidity index (THI: 75.8) of August (P1) was higher (P < 0.001) than that (69.7) of September (P2), although maximum ambient temperature (27.8°C) of P1 was numerically higher than that (26.3°C) of P2 without statistical significance. Glycerol supplementation did not affect both concentrate and forage intake, average daily gain (ADG), and feed/gain ratio at P1 and P2. ADG was lower (P = 0.03) at P2 (0.74 kg/d) compared with P1 (0.89 kg/d). Feed/gain ratio was improved (P < 0.001) at P2 compared with P1. Glycerol supplementation did not affect blood concentrations of glucose, triglyceride (TG), cholesterol, high-density lipoprotein (HDL), low density lipoprotein (LDL), nonesterified fatty acid, and albumin. Blood concentrations of TG, cholesterol, HDL, LDL, glucose, and albumin were lowest (P < 0.05) at late July compared with other times (August and late September). Glycerol supplementation decreased blood CD8+ T cell population at late July and mid-August. However, it did not affect other blood immune cell populations. Blood granulocyte to lymphocyte ratio was highest at August 27. Monocyte and B cell populations were lowest (P < 0.05) at August 11. In conclusion, glycerol supplementation did not affect growth and blood metabolic parameters. Feed efficiency was lower at higher THI August compared with September. Some blood metabolic and immunological parameters were influenced by ambient temperature.