Water is a critical resource whose availability and proper use is a key factor to Kenya’s sustainable agricultural development. However, changing climatic conditions and growing population in arid and semi-arid lands have exerted pressure on the scarce water resources. Consequently, there have been renewed efforts to enhance capacity of smallholder irrigation farmers to own and manage irrigation schemes. The objective of this study was to evaluate the farmers’ willingness to pay and to determine the average economic value of irrigation water used by major crops grown in the Kerio valley basin. A multistage sampling method was used to select a representative sample of 216 smallholder irrigation farmers. Data was obtained using a structured questionnaire administered to the farmers additional data on irrigation water requirements was obtained from the Food and Agriculture Organization Aquacrop model. The findings revealed significant differences in farmers occupation status, education level, total livestock ownership, membership in water users’ association, access to training, distance to the market and distance to the water source between farmers willing to pay and those not willing to pay. The results of the probit regression model indicated that the education level of household head, membership in irrigation water users’ association, farmers’ participation in the construction and maintenance of the scheme and total income from irrigation positively influenced the farmers’ decision on willingness to pay for irrigation water. However, distance to water source and access to extension services negatively influenced farmers’ decision to pay for irrigation water. The Contingent valuation model results indicate that 91.4% of the smallholder farmers were willing to pay for irrigation water with a mean willingness to pay of KES 938 (USD 10.4) per Ha in a production season. This represents about 9.6% of the average total farm income. Factors that positively influenced the mean willingness to pay are; age of farmers, household size, distance to the water source and income obtained from irrigation farming. The residual imputation model results on the economic values of irrigation water for nine crops indicate that the overall mean value is KES 11.5 per cubic meter of water. The economic value of irrigation water for the crops; sorghum, green grams, maize, millet, cassava, cowpeas, mangoes, bananas and lemons were KES 25.2, 20.9, 14.9, 3.6, 4.3, 2.7, 16.9, 7.4 and 6.5 respectively. The study recommends the implementation of an all-inclusive bottom up approach, water management system that ensures equitable and affordable water distribution to the smallholder farmers.