Abstract: Effect of replacement of inorganic minerals viz., zinc (Zn), copper (Cu) and manganese (Mn) with their corresponding organic minerals (methionine) on growth, bioavailability and immunity was studied in grower birds (9th to 20th week). At 20th week, the body weight of grower birds were significantly (p<0.05) higher in 100% organic Zn group, 100 and 50% organic Zn, Cu and Mn supplemented groups. The cumulative feed consumption and FCR of all the treated groups showed no significant (p>0.05) difference. The serum glucose, after cholesterol SGOT, SGPT and ALP levels differ significantly (p<0.05) of all the treated groups of differed significantly (p<0.05). The CBH response and the antibody titers against SRBC were found to be significantly higher in 100% organic Zn group and 100% Zn, Cu and Mn supplemented groups. Tibia bone weight (g), tibia calcium (%) and tibia phosphorus (%) varied insignificantly (p>0.05). But significant (p<0.05) difference was observed as regard to the tibia ash content. Faecal excretions of Zn, Cu and Mn were significantly lower in organic mineral fed groups. Replacement of inorganic Zn, Cu and Mn with their corresponding organic minerals improved the body weight and immunity, with lower faecal excretion of minerals in grower birds.