In order to improve mutton production, Dorset x Mandya and Dorset x Nellore halfbred rams were mated with Mecheri ewes to produce Dorset x Mecheri x Mandya and Dorset x Mecheri x Nellore quarterbreds. Least-squares analyses of the body weight of crossbred (n = 541) and purebred (n = 959) Mecheri sheep were made. The overall means for bodyweight of crossbred Mecheri sheep at birth, three, six, nine and 12 months of age were 2.27 ± 0.05, 7.97 ± 0.24, 11.84 ± 0.38, 14.73 ± 0.48 and 17.55 ± 0.56 kg, respectively and for purebred Mecheri sheep the values were 2.27 ± 0.02, 7.80 ± 0.10, 11.48 ± 0.15, 14.04 ± 0.17 and 16.23 ± 0.18 kg, respectively. Crossbreds had higher body weight than purebred Mecheri sheep at all age groups. However, it was not significant up to nine months of age. In general, period of lambing and sex of the lambs had significant effects on body weight of both genetic groups at different ages. The estimates of heritability for body weight ranged from 0.177 ± 0.129 to 0.338 ± 0.176 among different age groups. Highest heritability estimates were obtained for body weight at three and six months of age, hence these traits may be considered as selection criteria for improving the body weight of Mecheri sheep at different age groups.