This study investigated the effects of using different online instant response systems (IRSs) on students, particularly in remedial mathematics classrooms. To achieve the goals, this study applied a mixed-methods approach to examine the effects on learning performance, intrinsic motivation, and self-efficacy. The participants were the seventh-grade junior high school students; they were randomly divided into three experimental groups, Kahoot-based IRS, Quizlet-based IRS, and control group. The results indicated that students in the Kahoot-based IRS performed significantly better in mathematics learning performance and reported higher learning interests, choice, and group self-efficacy. Meanwhile, students in the Quizlet-based IRS remedial classroom reported more positively on learning interest, value, effort, and choice than to the control group.