Weak interactions are not negligible in layered structures and contribute strongly in their physical behaviors. Thanks to NL-vdW functionals and analysis methods of the electron density, their analysis is possible, which allows to better understand their effects on the different physical properties of solids. We have studied the role of weak interactions on structural properties, mechanical stability and optoelectronic behavior of LiGaTe2 under hydrostatic pressure effect. This study has shown that the contribution of weak interactions is not negligible in LiGaTe2. It has also been found that LiGaTe2 loses its mechanical stability by exceeding 5.64 GPa. NCI Analysis method has shown that weak repulsive interactions are more dominant than attractive ones and Li-Te bond has a strong ionic character, while Ga-Te bond is covalent. The optical properties for the different pressures have been studied by analyzing the variation of the dielectric function and that of the absorption coefficient.