The goal of this study was to investigate the effect of intravenously injected Mn from different Mn sources on tissue Mn concentration, heart Mn-containing superoxide dismutase (MnSOD) activity and its gene expression in broilers, so as to detect differences in Mn metabolic utilization among Mn sources. On d 22 posthatching, a total of 180 chicks were randomly allotted by BW to 1 of 5 treatments in a completely randomized design. The 5 treatments included a 0.9% NaCl injection solution without Mn addition (the control), a 0.9% NaCl solution with Mn sulfate or one of 3 organic Mn sources with weak, moderate, or strong chelation strengths at a dosage calculated according to the dietary Mn requirement of 120 mg/kg, Mn absorbability of 1.5%, and daily feed intake. Heart and bone samples were collected from broilers on d 10 and 20 after Mn injections for analyses of tissue indices. The results showed that on both d 10 and 20 after Mn injections, the birds injected with Mn-containing solutions had greater (P < 0.01) Mn concentrations in both heart and bone, heart MnSOD activities, and MnSOD mRNA levels than those injected with the control NaCl solution; however, intravenously injected Mn always had a sensitive and consistent effect on heart MnSOD mRNA level of broilers, and the birds injected with a solution containing the organic Mn source with moderate chelation strength always had the greatest heart MnSOD mRNA level. The results indicated that intravenously injected Mn from the organic Mn source with moderate chelation strength was the most utilizable Mn source and functioned in the sensitive target tissue more effectively than Mn from Mn sulfate or other 2 organic Mn sources with weak or strong chelation strength.