The FT-IR spectra of 2-(4-Isobutylphenyl) propanoic acid were recorded in the region 4000–450 cm-1. The quantum chemical calculations of geometrical structure and vibrational wavenumbers of 2-(4-isobutylphenyl) propionic acid (abbreviated as 2IPA) were carried out by B3LYP level with 6-311G (d,p) and 6-311++G (d,p) standard basis sets. The complete vibrational assignments of wavenumbers were performed on the basis of potential energy distribution (PED). The vibrational modes were calculated using vibrational energy distribution analysis VEDA 4 program. The UV-Vis spectrum was recorded in the region 400–200 nm.