Understanding the optimal planting time and cultivar selection can significantly enhance cotton production efficiency and sustainability. Such insights are crucial for farmers and agricultural planners to make informed decisions that maximize productivity and economic returns. This study aimed to investigate the effects of different planting dates on the phenological development, growth, and seed cotton yield of two cotton cultivars (FH-142 and CIM-616), as well as to simulate these effects using modeling for better crop management. A study conducted at the Central Cotton Research Institute in Multan, Pakistan, the field experiment utilized a randomized complete block design with split-plot arrangement and three replications. The planting dates were April 1, April 15, and May 1. Results showed that CIM-616 superior performance with the maximum leaf area index (LAI) (4.45), leaf area duration (LAD) (444.55 days), total dry matter (TDM) (1540 g m-2 ), crop growth rate (CGR) (9.88 g m-2 d -1 ), and net assimilation rate (NAR) (3.35 g m-2 d - 1 ) when planted on April 1, followed by April 15, and the least on May 1. Phenological observations revealed that CIM-616 planted on April 1 took the longest duration to reach various growth stages and had the highest plant height (134.33 cm), number of bolls (47), sympodial branches (57), and seed cotton yield (3467.33 kg ha-1 ). Additionally, the CROPGRO-Cotton model was calibrated and evaluated using the field data. The model's predictions for phenology, LAI, and yield closely matched the observed values, with RMSE values indicating good agreement (e.g., RMSE for days to anthesis was 4.47 for FH-142 and 5.83 for CIM-616). The calibrated model accurately simulated the days to anthesis, maturity, and yield at different planting dates, demonstrating its applicability in predicting cotton growth and yield under varying climatic conditions. The study concluded that early planting (April 1) combined with the CIM-616 cultivar resulted in optimal growth and highest yield, emphasizing the importance of planting time and cultivar selection for maximizing cotton yield in the given agro-ecological conditions. The CROPGRO-Cotton model proved to be a valuable tool for simulating and optimizing cotton production.