Successful maize cultivation requires an understanding of various management practices as well as environmental conditions that affect crop production. Sowing time is the most important non-monitory input subjected to variation due to the difference in weather at sowing time. Delay in sowing beyond a given date results in a progressive reduction in the yield since crop experiences excess moisture stress due to high rainfall, low temperature and high relative humidity during early stage. CERES-Maize model was calibrated using experimental data to evaluate the ability of CERES-Maize model to simulate the effect of planting window and nitrogen levels on growth and yield of maize (Zea mays L.) under irrigated conditions. Model validation confirmed that, model can be used as a research tool under irrigated conditions up to 21 July sowings to guide alternate ways of improving maize production in different agro climatic zones of Telangana State as the model simulation for phenology and physiological maturity was considered as excellent with NRMSE value being less than 10%. Whereas, simulation of LAI, number of grains per cob, grains m-2 and grain yield was considered as good with simulation values ranging in between 10.1 to 20%. Further calibrated model was used to identify the optimum sowing window and nitrogen level for irrigated maize using DSSAT seasonal tool using 30 years historical daily weather data from 1981 to 2010. Based on seasonal analysis, optimum sowing window for irrigated maize would be from 6 July to 27 July and optimum nitrogen would be 250 kg ha-1.