A field experiment was conducted on a Bayamón soil to evaluate the effect of foliar applications of nitrogen, potassium and magnesium on the yield and quality of pineapple cultivar Red Spanish. The application of 392 kg/ha of K and 224 kg/ha of Mg resulted in a significant increase in fruit yield over the lowest K-Mg application rate (224 kg/ha of K and no Mg) in the plant crop. Increasing N from 224 to 392 and to 784 kg/ha did not significantly increase fruit yield but reduced brix and acidity and increased pH of the fruit. A significant increase of 6,572 kg/ha of pineapple fruits was obtained in the ratoon crop with the application of 520 kg/ha of K and 74 kg/ha of Mg. Nitrogen levels had no significant effect on pineapple fruit yield and quality in the ratoon crop. The average length and width of the fruit and core diameter increased significantly as magnesium applications increased. Nitrogen and potassium content of the D-leaf of 4-month-old plants was adequate, but rather low in 10-month-old plants, regardless of N-K treatment. In the ratoon (22- and 26-month) leaf nitrogen was adequate, but potassium was low. Potassium treatments had little effect on leaf potassium content. Calcium and magnesium content ran low throughout the crop cycle, especially in the ratoon crop.