The effect of partial replacement of KCl in the fertigation by KCl.MgCl 2 on growth, yield and quality of greenhouse tomato (cv. Durinta) was studied in a soil-less system. Forty-seven days after planting (DAP), three treatment solutions were applied to the plants using different K sources: (1) KNO 3 , (2) KCl, and (3) KCl.MgCl 2 +KCl (25%:75% in terms of K supplied). In both treatments 2 and 3, NH 4 NO 3 , Ca(NO 3 ) 2 and HNO 3 were added as source of N. Plant height and total chlorophyll were the highest in the KCl+KCl.MgCl 2 treatment. Leaf Mg content was significantly lower in the KCl treatment, whereas highest in the KCl+KCl.MgCl 2 treatment. Both KCl and KCl+KCl.MgCl 2 led to a significantly higher leaf Cl content as compared with the KNO 3 treatment, but no Cl toxicity was observed in either treatment. Total yield was not different among treatments. Fruit firmness and freshness of the calyx were significantly improved by KCl and KCl+KCl.MgCl 2 , and the number of rotten and blotchy fruits were significantly reduced by both these treatments. KCl+KCl.MgCl 2 also led to significantly higher levels of glucose, Mg and dry matter content in the fruit. Lower NO 3 and higher Fe contents were measured in both treatments 2 and 3. Although KCl as sole K source showed lower foliar Mg level as compared to KNO 3 , the use of the KCl in tomato fertigation improved tomato fruit appearance and qualities. However, 25% replacement of KCl by KCl+KCl.MgCl 2 increased the foliar Mg level and improved fruit qualities even further.