Potato is a cash money crop and plays a crucial role in Egyptian economy, but for its best growth; it demands a good fertilization program as N, P and K. Therefore, this study was conducted to find out the effect of potassium fertilizer levels, in specific, some cultivars on vegetative growth, yield and quality of potato (Solanum tuberosum L.). The investigation was conducted in a private farm during the two successive years of 2015 and 2016 in Maghnine village, Kom Hamada, El-Behera Governorate. Each experiment was laid out as split-plot design, with three replications for both seasons. Three cultivars; Spunta, Provento and Galactica were distributed in the main plots, while the potassium levels; 0,50,75 and 100 kg K₂O fed^-1 were distributed in the sub-plots. The obtained results revealed that there were significant differences in the performance of the tested cultivars, regarding yield and quality parameters especially, cultivar “Galactica" which was found to be more responsive and had high yielding, where it gave the best results in most of the studied parameters. Application of potassium especially at 100 kg K₂O fed^-1 led to the highest values of plant height (cm), plant yield (g), average of tuber weight (g), total tubers yield (ton fed^-1), tubers specific gravity, tubers total and reducing sugars content (%) and tubers starch content (%).  Thus, it is, recommended that we should introduce potassium fertilizers to optimize productivity of potato in Egypt.