Learning fractions is important for both academic and functional mathematics. However, many students including students with developmental disabilities struggle with solving mathematical fractions problems. To support students with developmental disabilities in learning fractions, the purpose of this study was to explore the effectiveness of the virtual manipulatives based instructional sequence on the acquisition and maintenance of computations with fractions(i.e., adding fractions with unlike denominator). A total of three middle school students with developmental disabilities participated. Using a multiple probe design across participants, a functional relation was found between the intervention and the accuracy of solving adding fractions problems for each student. All students acquired the targeted skill and maintained their performance up to three weeks.