The aim of this study was to investigate the effects that supplemental irrigation (SI) has on Kale (Brassica Oleracea) crop yields as compared to wholly rain-fed crop. The experiments were conducted in Kieni, Central Kenya where the rainfall pattern was bimodal. The planting for rain-fed crops was done in three blocks each measuring 10m x1m with a spacing of 30cm between plants and 45cm between rows of plants and the procedure repeated for the crops receiving SI. The average weekly yields were computed for both crops for each season comprised of 14 weeks. The average weekly yields were subjected to Analysis of Variance (ANOVA) to determine whether the average yields from rain-fed and supplemental irrigated crops were statistically different. This was done by MS Excel 2016 spread sheets by setting a statistical level of significance of 5%. F value was 17.94 higher than the critical value of 4.01 while the P-value of 9x10-5 was lower than the 5% level of confidence meaning that there was a significant difference in the yield means of rain-fed and SI crops. The total rain-fed crop yields for the period was 147.0 Kgs and that of the one under SI was 238Kgs, an increase of about 62%. Therefore, supplemental irrigation can be adopted in areas where rainfall trends are declining to increase crop yields when all other factors remain constant for farmers to increase resilience.