We evaluated the growth performance of wild and cultured (four generations) strains of giant freshwater prawn (GFP) in 2 x 2 diallel crosses. From the four cross combinations, juveniles were produced using single pair mating. A total of 3,840 prawns (1,528 males and 2,312 females) were harvested after 15 weeks of grow-out in hapas. Additive genetic estimates of the crosses showed that wild stock had higher length (TL) and weight (BW) (12.17% and 22.33%), while the cultured stock had lower length and weight (−18.26% and −22.98%). Heterosis in the crossbred stock increased (TL:0.84 and BW:6.70%) with reduced carapace length (CL:1.34%) along with more than 5% increased additive genetic effect on body weight when compared with that of both purebred stocks. Genetic diversity data obtained for the wild, cultured, and crossbred stock using five microsatellite loci showed increased heterozygosity with decreased inbreeding in the crossbred stocks when compared with the cultured stock.