Diffusion of modern irrigation systems is one of the most important objectives of Iranian water policies targeting the sustainable use of water resources to resolve the water crisis. Despite considerable policy support, high subsidization, and a range of benefits, farmers have only minimally adopted modern irrigation systems in most parts of Iran. Therefore, the water crisis persists in almost all parts of the country. Thus, decision makers must recognize why diffusion of these systems has not been successful among farmers despite strong financial and political support. The aim of the current study was to investigate differences between adoption groups of modern irrigation systems and more critically whether the aspects affecting approval were altered by ongoing diffusion prejudiced by policy support. In other words, we explored the postponement of adoption among the early and the later adopters of modern irrigation systems and aimed to identify reasons behind different adoption behaviors. To achieve these aims, we developed a research framework of adoption that integrates multiple theories. In addition to the already established measures (human and physical capital), the current study integrated social capital and technology characteristics. A cross-sectional survey was carried out in Behbahan district in Khuzestan province southwest Iran. A total of 274 farmers were interviewed, of which 100 farmers had not and 174 farmers had adopted modern irrigation systems. A multinomial logit model was applied by using STATA14 to identify the most effective factors for farmers’ adoption decisions. We distinguished four groups; three consisted of adopters (early, middle, and late adopters) and a fourth group of non-adopters who did not accept modern irrigation technologies. The study found that farmers’ delayed adoption of drip irrigation technologies was due to the complexity of the application process and the availability of family and work social capital. Additionally, the study suggested that improved trust in institutions could increase the likelihood of earlier adoption of these technologies. The results also revealed divergent perspectives among pioneer (early adopters), follower (middle adopter), and laggard (late adopter) farmers regarding the adoption of drip irrigation technologies.