The purpose of this study was to examine the effects of "Understand and Solve!" Strategy on change problems including change of a one-step addition and subtraction of children with mild intellectual disabilities and whether they maintained their achievements 3, 5, and 8 weeks after the intervention. Moreover, the effects of the Understand and Solve! Strategy on generalization to different types of problems and multiple step problems as well as on the perception, attitudes, knowledge, use, and control of problem solving strategy were investigated. Three students with intellectual disabilities who were 11 to 12 years old and attended 5th grade participated in the study. "A Multiple Probe Design Across Subjects," which is one of the single subject research designs, was used in the study. The findings of this study showed that Understand and Solve! Strategy was effective in teaching students with mild intellectual disabilities solving change problems including one-step addition and subtraction, they maintained their skills and generalized their skills to different problem types, two-step change problems. As a result of the intervention, students' perception and attitudes towards mathematics as well as knowledge, use and control of strategies to solve mathematical problems positively changed.