The study examines the effectiveness of the Form Four STEM-Based Physics Interactive Laboratory (i-Lab) to enhance form four students' achievements in Physics. It describes the design process by employing the Isman Instructional Design Model. A quantitative study was carried out using an experimental method. The instruments used were pretest and posttest for form four students' achievements in Physics. The sample of this study consists of three groups: a Traditional Physics Laboratory (T-Lab); Form Four STEM-Based Physics Interactive Laboratory with explanation feedback (i-LabP); and Form Four STEM-Based Physics Interactive Laboratory with knowledge of results (i-LabK). In this study, T-Lab is control groups while i-LabP and i-LabK are treatment group. Each group had 20 participants. Statistical analysis in the form of One Way Anova was used to compare the achievements of students in each group (T-Lab, i-LabP & i-LabK). The findings show that i-LabP had highest score mean at 64.70, followed by i-LabK at 56.90 and T-Lab at 52.65. The findings from this study suggest that the Isman Instructional Design Model is suitable in the development of Form Four STEM-Based Physics Interactive Laboratory (i-Lab) to enhance form four students' achievements in Physics.