Feeding experiments were conducted to determine the bioavailability of new types of manganese (Mn) supplement to rainbow trout fingerlings. Two levels of Mn (7 and 14 mg kg−1 diet) were supplemented to diets using either manganese sulphate (Mn‐S), glass‐embedded Mn (Mn‐Gl), or amino acid‐chelated Mn (Mn‐Am); more than one acid was used to chelate the metal. Rainbow trout weighing 1.30 g on average were fed the experimental diets for 12 weeks. Absorption of Mn from various compounds was evaluated using larger fish (105 g on average) fed the experimental diets. Growth was higher in the group supplemented with Mn‐Am at both levels. Whole‐body Mn content in fish fed the diet supplemented with Mn‐Am was significantly higher than the other sources. Bone Mn accumulation was significantly higher in treatments with 14 mg Mn kg−1 diet from all sources, except Mn‐Gl. At 7 mg kg−1, absorption from Mn‐Am was significantly higher than from Mn‐Gl and Mn‐S. Mn retention from both levels of Mn‐Am supplementation was significantly higher (P < 0.05) than the rest. The results indicated that amino acid‐chelated Mn provided more bioavailable nutrient than Mn‐S and Mn‐Gl. Further, availability of Mn from Mn‐Gl is equivalent to that of Mn‐S.