Tanzania is located in east Africa and has a population of 51 million people; by 2050 the population is expected to be two and a half times larger. It is one of the poorest countries in the world with per capital annual gross domestic product of $3,000, making it the 188th poorest country in the world. The major source of national income comes from agriculture, which employs about 80 percent of the working age population. Smallholdings dominate agriculture production in Tanzania, each with an average size of 2 hectare. However, only about 25 percent of the arable land is farmed and 0.5 percent is irrigated. The lack of irrigation, poor irrigation practices and poor water management are among the factors that affect crop production for smallholder farmers in Tanzania. Rainfall is variable and uncertain and poor irrigation practices lead to problems such as waterlogging, water loss, and uneven water access in a field. Yields per hectare are about one fifth of those in the United States and half those in India. Many projects by non- government organizations and Kilimo Kwanza (Agriculture First) initiated by the government, have been established to help smallholder farmer to increase their crop production by improving water management, providing education of best farming. practices, including irrigation practices, and aiding in increasing the use of irrigation. However, resources are scarce and there is a need for decision and design tools to improve irrigation practices and having better water management to meet the rising demands of food. Therefore, the focus of this research study was to improve irrigation practices in Tanzania by developing an Irrigation Decision Support Tool (IDST) that: (1) provides guidance on water application and management; (2) plans an irrigation schedule based on soil- moisture conditions of a field; (3) determines if irrigation is viable in a field; and (4) helps farmers to select an appropriate irrigation type to use in their field. The expectation is that using the IDST will improve crop quality and quantity by providing more consistent and more favorable soil-water growing conditions. The IDST includes Geographical Information System (GIS) layers that are selected by the user clicking on a location on a map of Tanzania or entering the coordinates of the location. The main challenges in developing the IDST were creating data layers of climate, soils, crop attributes and irrigation system components for a range of different irrigation practices. The IDST provides specification for a user selected irrigation practice; the irrigation interval, application time and application rate and water needs. Future work will add a cost-benefit analysis.