The academic self-concept (ASC) is a domain-specific construct, which plays an influential role in academic motivation and choices. Although some ASC models and instruments have been developed for mathematics and science, none have been specifically designed to measure the physics ASC. Therefore, this study focuses on designing and validating a model for measuring the physics ASC. In the proposed model, students' physic academic self-perception is measured by a novel instrument called Physics Academic Self-Concept Inventory (PASCI) based on domain-specific learning targets. The major physics learning targets considered in the PASCI design are physics knowledge, attitudes toward physics, and physics-related skills. Confirmatory factor analysis and psychometric methods are used to test and validate the proposed model and the PASCI instrument on the data collected from 861 male and female students attending secondary high schools in Iran. The results indicate that the devised model has appropriate fit measures and robust structural validity so that in multiple group analysis, model parameters are invariant. The author suggests that the idea of physics ASC should be modeled as a hierarchical and multidimensional structure based on physics learning targets to be effectively helpful to physics education researchers and teaching physics in classrooms.