A field study was carried out to evaluate the application of DSSAT model for simulating the impact of planting densities and nitrogen rates on growth, yield and quality of sunflower hybrids. The experimental data needed to run the model was obtained from two years (2010 and 2011) field experiments at two locations, including the Agronomic Research Area, University of Agriculture, Faisalabad and Research Area of University College of Agriculture, University of Sargodha. The achene yield among various treatments (hybrids, planting densities and nitrogen rates) was associated with growth and development of crop or to their photosynthetic activity. At both the experimental locations, the nitrogen rate 150 kg ha-1 and planting density 83, 333 plants ha-1 (20cm plant spacing) gave higher yield as compared to standard 125 kg N ha-1 and 66,666 plants ha-1 (25cm plant spacing), respectively. Similarly, S-278 performed well, in term of achene yield and achene oil contents at both locations than Hysun-33 sunflower hybrids. The DSSAT (OILCROP-SUN) model testing and application in this study established that this specific model could be satisfactorily used as a research tool at different locations of Punjab-Pakistan. The DSSAT (OILCROP-SUN) model was calibrated and evaluated under local conditions and it predicted phenology, growth and yield of sunflower crop to a reasonable accuracy for different sunflower hybrids at varying planting densities and nitrogen application. The findings propose that the model can be used to direct the alternate path for improving sunflower production in different agro-environmental conditions of the Punjab, Pakistan. At the end, following suggestions must be under taken to meet the future challenges. Simulation of other crop nutrients (P&K), irrigation scheduling and cropping system research should also be focussed in modeling studies. Inter comparison of different models should be carried out to simulate the growth and yield of sunflower under semiarid environment of Pakistan. Optimization of site specific production technology for different crops using crop growth models should be tested and promoted. Future studies for possible impact of climate change on new hybrids of sunflower and other crops production should be included at more number of weather stations to better reflect the heterogeneity in different cropping regions.