Poultry products are among the best sources of animal protein for human consumption, and offers a solution to animal protein shortage, especially in Nigeria and other African countries. The aim of the study was to assess the body weight and growth traits of the Nigerian heavy local chicken ecotype selected for generations G7 and G8 through selection index. A total of 350 and 345 day-old chicks for generations (G) 7 and G8, respectively, were used for the study. Generation G7 chicks were produced from the existing generation G6 parent stock, while G8 chicks were generated from G7 parents, in the Teaching and Research Farm, Department of Animal Science, University of Nigeria, Nsukka. Thirty (30) mature cocks and 90 mature laying hens were randomly chosen from the G6 parent stock, and randomly divided into six mating/breeding groups at mating ratio of 1 male: 3 females, to produce the G7 chicks. Artificial insemination was used to inseminate the hens. Semen collected from the males were used to inseminate the females according to the mating ratio and breeding groups. The insemination was done on two days interval and lasted for two weeks. Fertile eggs were collected, incubated and hatched according to mating groups to produce the contemporaneous aged chicks for the study. Similar protocol was applied to generate the chicks for G8 study. Generation G7 chicks were produced from G6 parents, while, G8 chicks were produced from G7 parents. Feed and water were provided to the birds ad libitum. Data were collected on body weight at 4 weeks interval. Data on feed intake were collected on daily basis and finally used to calculate the feed conversion ratio (FCR). Data collection lasted for 24 weeks. The data were subjected to analysis of variance and significant means separated using Duncan New Multiple Range Test. The results of the growth traits showed that initial body across generations G7 and G8 were not (p>0.05) significant on sex, but, significantly (p<0.05) influenced by the breeding groups. Final body weight increased significantly (p>0.05) across sex and mating groups. The results indicated that male birds were better feed converters compared to their female counterparts across generations G7 and G8. The overall body weight of the birds at hatch were not (p>0.05) significant across generations G7 and G8, but, showed significant (p<0.05) differences across the mating groups. The overall body weight at week 24 of age were 1352.11±17.39 and 1605.67±18.13 for generations G7 and G8, respectively. Body weight of male chickens were progressively higher than those of the females from hatch to week 24 of age, similarly, generation G8 birds showed superiority over the G7 birds throughout the experimental period. It was therefore, concluded that continuous selection can lead to further genetic progress, so long as there are still reasonable variation among the populations of the Nigerian heavy local chicken ecotype.