Oils derived from oil-bearing seeds or certain fruit pieces are known as plant oils or vegetable oils. Using the Soxhlet extraction technique and n-hexane as the solvent, Thevetia peruviana seed oil was extracted from the seed flour. Its physicochemical parameters were determined using standard analytical methods. The hydroxylation process was done through the vigorous stirring of the oil and formic acid with the slow addition of peroxide. The hydroxylated oil was analyzed for functional groups present using Fourier Transform Infrared Spectrometer. The results of the physiochemical parameters showed that Thevetia peruviana oil has acid value (3.88 mg KOH/g), iodine value (93.5 Wij’s), peroxide value (30.0 meq/kg), kinetic viscosity (1.6cp) and saponification value (121.76 mgKOH/g) while the hydroxylated oil has acid value (0.77 mg KOH/g), iodine value (81.40 Wij’s), peroxide value (7.85 meq/kg), kinetic viscosity (7.43cp) and saponification value (162.05 mgKOH/g). The FTIR results showed that both non-hydroxylated and hydroxylated plant oils had the following functional groups OH, CH, C=C, CH2, and C=O. The results showed that the bands were shortened in the hydroxylated oil spectrum except (OH) which became broad indicating the formation of the hydroxyl group by the consumption of the C=C band in the unhydrolyzed oil. The hydroxylation of plant oils using Thevetia peruviana shows the potential of the plant oil to be used as a precursor for the production of industrial intermediates which can replace the dependence on petroleum products.