Developing healthy plants is necessary for maximum growth and this requires all essential nutrients to be supplied at optimal rates. So, two field experiments were conducted in a calcareous soil at Nubaria Agricultural Research Station, El-behera governorate, Egypt (Latitude 30^o 54' 48.220" N, Longitude 29^o 51' 50.634" E), during 2014/015 and 2015/016 winter seasons to assess the effect of potassium (K₂SO₄) and magnesium (MgSO₄ 7H₂O) fertilizers applied separately or in combination on yield and some qualitative parameters of potato (cv. Alpha) tubers. The two experiments were laid out in a randomized complete block design with three replicates including fifteen treatments as follows: 0, 24 and 48 kg K₂O fed^-1 and 0, 5, 10 & 15 kg Mg fed^-1.The last three treatments contained 2.5, 5 & 7.5 kg Mg fed^-1 combined with 24 kg K₂O fed^-1 plus foliar application of 1% K₂O + 0.63 % Mg. The obtained results show that the combination of both nutrients (K and Mg) as 24 kg K₂O fed^-1 plus 15 kg Mg fed^-1 significantly increased number of tubers plant^-1, tuber yield plant^-1, medium sized tuber yield (35-55mm) and total tuber yield as well as tuber quality i.e. total carbohydrate % & starch %, tuber dry weight and N, P, K & Mg uptake in tubers over the control (zero K and Mg fertilizers). On the other hand, the highest large sized tuber yield (<55mm) was obtained under the treatment received 48 kg K₂O fed^-1 combined with 5 kg Mg fed^-1 which did not differ significantly from treatment received 24 kg K₂O fed^-1 plus 7.5 kg Mg fed^-1 accompanied by foliar spray of 1% K₂O + 0.63 % Mg, whereas soil application of (24 kg K₂O fed^-1 plus 5 kg Mg fed^-1) or (24 kg K₂O fed^-1 plus 7.5 kg Mg fed^-1) accompanied by foliar spray of 1% K₂O + 0.63% Mg recorded higher significant increases in leaf N content and dry matter % of tubers relative to control treatment with no significant difference between the two treatments. The highest values of P and K content in leaves were obtained when plants were treated with 48 kg K₂O fed^-1 solely, while applying 15 kg Mg fed^-1 alone gave the highest significant value of Mg content in potato leaves.