Using gamification in assessments makes learning more engaging and encourages students to participate actively in the classroom. This study investigates the effect of gamification-based formative assessment on academic achievement among primary school students in the context of mathematics learning. Randomized pretest-posttest control group design was utilized in a true experimental design. The target population of this study contained 10 schools, with 248 students in the 5th class in District Astore, which had internet access and an IT lab. A simple random sampling technique was applied to select the sample as a school from the target population. A pretest and posttest were conducted to gather data on mathematics achievement of cognitive skills. The study used Kahoot in gamification-based formative assessments to determine an improvement in postintervention academic achievement in mathematics among primary students. It was found that the experimental group had a significantly higher mean score (M = 25.52, SD = 1.74) compared with the control group (M = 14.59, SD = 2.17) with a large effect size (Cohen's d = 4.92), using gamified assessment improves cognition. It implies the extent to which gamification has a positive influence on students' interaction, learning, and success in mathematics. To improve mathematics learning, educators in schools should incorporate games, such as Kahoot, because they are fun, reduce pressure, and increase success. Future studies may be conducted on whether gamification-based formative assessment practices effectively improve the higher-order cognitive skills of students toward mathematics teaching.