A complete 3x3 diallel cross experiment involving 3 chicken breeds namely Aseel Peela (AP), Kadaknath (KN) and CARI-Red (CR) were used for comparison of performance of pure and crossbred chickens for body weight gain and to estimate the relative importance of different types of gene action involved in the inheritance of these trait. The chicks were brooded up to 6 weeks of age in four tiers battery cage brooder then shifted to deep litter and managed with ad libidum feeding and watering. Gain in body weight was calculated at biweekly interval up to 20 wks of age. Further, data were subjected to combining ability and other effects analysis using important models namely, Griffing (1956), method 1 under model 1. Among the purebreds CR had higher body weight gain in male, female and combined sex at 0 to 20 wk of age except, at 15-16 and 19-20 wk of age AP had higher body weight gain in combined sex. Among the cross bred, cross AP x CR had highest body weight gain in combined sex at 0-8, 0-16 and 0-20 wk of age. The analysis of variance between mating revealed highly significant difference at all ages of measurement except at 11-12 wk of age, among genetic groups are also revealed highly significant difference at all ages of measurement in male, female as well as combined sex. It was observed that the overall performance for body weights gain in crossbred were significantly better than the pure bred performance. Body weight gain revealed highly significant difference for general combining ability (GCA) at all ages of measurement in male, female and combined sex except, at 17-18 wk of age in female. However, Analyses of variance for specific combining ability (SGA) revealed highly significant difference in irrespective of sex at all ages of measurement except, at 5-6 wk of age in female, 11-12 wk of age in male, female as well as in combined sex and at 19-20 wk of age in male and combined sex. Reciprocal effects were also significant at all the ages of measurement irrespective of sex except at 11-12, 15-16 and 19-20 wk of age in male. CR had higher and positive GCA estimates. While, lowest and negative value was observed in case of KN. The cross AP x KN had positive and highest value of SCA as well as reciprocal effects in case of male, female and combined sex at all the age of measurements.