This research was to examine the effects of the mathematics games for implement of dynamic assessment on adding operation abilities of students with intellectual disabilities. The design for the study were based on the multiple baselines across subject and modified mathematics game activities for learning model were applied for the treatment method. As the subjects, three students with intellectual disabilities were analyed and measured to evaluate the addtiion skills from every session. As the results of the study, the addition skills of students with intellectual disabilities had improved through the mathematics game activities and maintained even after the end of the treatment. The mathematics games for implement of dynamic assessment on adding may have positive effects on the development of mathematical abilities and mathematical process skills of students with intellectual disabilities.