We present a detailed first-principals calculation to study the elastic anisotropy, vibrational and optic properties of a AgScSi compound using the generalized gradient approximation method with the projector augmented wave method. Optical, elastic anisotropy and phonon properties of AgScSi under pressure were analyzed. The degree of anisotropy with pressure change was analyzed in 3-dimensions. The phonon dispersion curves were drawn with corresponding phonon partial density of states. The optical properties of the AgScSi compound were examined according to the pressure to explore further application properties. According to our calculations, AgScSi compound, a semiconductor material, is dynamically stable, which is favorable for optoelectronic applications.