Agronomic traits ultimately contribute to final achene yield and improvement in agronomic traits means increase in achene yield. A field trial was conducted at experimental area of Agronomy Department, PMAS Arid Agriculture University, Rawalpindi during 2008 and 2009 to evaluate the performance of two sunflower hybrids i.e S-278 and Hysun-33 under different levels of K application (0, 50, 100, 150, 200, 250 and 300 Kg ha-1). The experiment was laid out in randomized complete block design with three replications in split plot arrangement keeping K levels in main plot and sunflower hybrids in sub plots. It was observed that K application did not significantly improve plant height, head diameter, 1000-achene weight, achene yield, stalk yield and harvest index except number of achene head-1, where application of K showed significant improvement. Among sunflower hybrids, S-278 produced significantly taller plants, heavier 1000-achene weight, higher achene and stalk yield, but lesser harvest index than that of Hysun-33. Both hybrids were, however, similar for head diameter and number of achene head-1. Sunflower hybrid S-278 produced the highest achene yield when crop was fertilized with K @ 150 Kg ha-1 due to heavier 1000-achene weight. Similar trends were observed for stalk yield. Sunflower hybrid Hysun-33 produced the lowest achene yield when crop was grown with K. Hysun-33 produced the highest harvest index when crop was fertilized @ 100 Kg K2O ha-1. Similarly, S-278 produced the lowest harvest index when crop was fertilized @ 100 Kg K2O ha-1. It is therefore suggested that sunflower hybrid S-278 should be cultivated with K application @ 150 Kg ha-1.