Instructional material is an integral part of teaching and learning process. Validating instructional materials is imperative to ensure quality before widespread utilization. This study validated the developed Gamified Instructional Material (GIM) in genetics for grade 12 STEM students. It employed the descriptive-developmental research design involving 41 STEM students and 11 Biology education experts chosen through purposive sampling. Findings revealed that students and experts strongly agreed that the GIM satisfied the criteria for a sound and valid instructional material. Further, the significant change in the pretest and posttest scores of students indicated an improvement of their knowledge in genetics. It is recommended that the GIM be used as supplementary instructional material in teaching genetics.