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The age‐related morphological changes of the testes in light ecotype Nigerian indigenous chicken were evaluated in this study using gross anatomical, histological and histomorphometric techniques. The results showed that the testes of 3‐ to 9‐month‐old birds were light pink while testes of sexually mature chicken were creamy white in colour. The left and right testicular weight, length, diameter, circumference and the organosomatic indices increased significantly (p <.05) with increasing age across the groups. Although the mean tubular diameter and epithelial height of the left and right seminiferous tubules increased significantly (p <.05) with age, the tubular diameter, epithelial height and luminal diameter did not vary significantly (p >.05) between the left and right testes of all the groups. The one‐cell layer thick germinal epithelium of the left testes at 3 to 6 months old showed islands of cell proliferation that contained spermatogonia and spermatocytes. At 6 to 9 months, the left testes exhibited numerous early spermatids with occasional occurrence of late stage spermatids while the right testes showed scanty early stage spermatids. At 12 to 18 months, the germinal epithelia of both left and right testes were characterized by the presence of Sertoli cells, spermatogonia, primary spermatocytes, numerous early and late stage spermatids as well as spermatozoa. In conclusion, the morphological features highlighted in the present study show that at pre‐pubertal periods, the left testes may develop faster than the right testes. However, both left and right testes may participate actively in the production of spermatozoa during the post‐pubertal life. [ABSTRACT FROM AUTHOR]