Growth curve parameters in chickens can be affected by genetic and environmental factors. This study estimated the growth curve parameters of Ovambo (OV) and Black Australorp x Ovambo (BAO) chickens under a commercial (COM) and a Moringa oleifera leaf meal-containing (MOLM) diet. Thirty-two (32) BAO and 36 OV chicks were randomly allocated to eight pens and then the pens were randomly allocated the two diets giving rise to four treatment groups (BAO-COM; BAO-MOLM; OV-COM; and OV-MOLM). Chicks were weighed in groups of 4 from weeks 1–4; from 5–20 weeks chickens were individually weighed. The Logistic, Gompetz, von Bertalanffy and Richards functions were fitted to the data and the Gompertz function was the best fitting based on RMSE, AIC and BIC. The maturing rates, mature weights (g), age at inflection (d) and average daily gain (ADG) (g/d) were as follows: BAO-COM (0.0222 ± 0.0025; 3197.9 ± 196.5, 63.3, 25.8); BAO-MOLM (0.0142 ± 0.0036; 3783.4 ± 1031.3, 103.2, 17.3); OV-COM (0.0241 ± 0.0031; 2605.7 ± 159.0, 58.7, 22.3); and OV-MOLM (0.0159 ± 0.0037; 2952.9 ± 641.0, 95.5, 15.7), respectively. The results imply that the inclusion of M. oleifera led to higher mature sizes, but reduced the maturing rates and ADG compared to the commercial diet.