Size dispersion in farmed fish has a substantial impact on production's bioeconomic performance, directly affecting net profits. This work's objective was to develop a bioeconomic model based on experimental data to identify the optimal harvest time (OHT) for Nile tilapia Oreochromis niloticus. The bioeconomic model considered four minimum marketable sizes (Mms = 350, 400, 450, and 500 g). Organisms were selected by size with different coefficients of variation (CV). Therefore, they were reared under two growth strategies: heterogeneous size (HT = 44-155 g; CV 25.5%) and homogeneous size (HM = 87-112 g; CV 5.9%). The HT system-generated tradable biomass of 99.30% in an OHT of 196 days with a net profit of USD 3,551.61 and a Mms of 350 g. However, the HM system achieved greater marketable biomass (99.53%) in less time (OHT = 181 days) with a net profit of USD 3,327.96 for the same Mms. The Mms of 500 g had the lowest net benefit in both systems. The HM strategy earned an additional 10.66% of incomes, indicating that the reduction in size dispersion positively impacted profits. The developed model provides a new perspective regarding the management of heterogeneity and size homogeneity in commercial production of Nile tilapia in intensive systems.