Potassium has significant effect on quantity and quality of tomato yield because of its vital roles in photosynthesis, favoring high energy status and appropriate nutrient translocation and water uptake in plants. However, little is understood or it is being overlooked under Eritrean condition. Besides, poor soil fertility is among the major production constraints in Eritrea. The field experiment was therefore conducted to investigate the effect of potassium levels on productivity and fruit quality of tomato at Hamelmalo, Eritrea. The experiment was conducted in Randomized Complete Block Design with nine potassium levels (0, 50, 100, 150, 200, 250, 300, 350 and 400 kg K 2 O/ha) replicated thrice. Data was collected on yield and fruit quality parameters and they were subjected to one-way analysis of variance (1-way ANOVA). The results of this study revealed that potassium had significant effect in all yield and quality parameters studied. Fruit diameter, fruit weight per plant, total yield, total soluble solids, specific gravity and fruit dry matter content showed significant increase with an increase in potassium level from 0 to 150 kg K 2 O/ha and thereafter decreased while fruit moisture content was increased in the range of 150 -400 kg K 2 O/ha. As a result, highest fruit weight (1.39 kg/plant), fruit yield (15.45 t/ha), total soluble solids (3.84 o Brix), specific gravity, (1.46) and fruit dry matter (5.68%) were recorded from 150 kg K 2 O/ha. Therefore it is recommended that potassium fertilizers should be used and balanced NPK fertilizers should be applied to improve yield and quality of tomato produced.