To protect holy basil essential oil (HBEO) from volatilisation and oxidation, microencapsulation by simple coacervation of gelatin was developed. An optimal encapsulating condition obtained from response surface methodology (RSM) was a gelatin concentration of 11.75% (w/v) and an HBEO amount of 31 ml, which provided the greatest yield, oil content, and encapsulation efficiency of 98.80%, 66.50%, and 95.41%, respectively. Scanning electron microscope (SEM) revealed that the internal surface of the microcapsule was honeycomb-like networks containing nonhomogeneous distributions of HBEO. Fourier transform infrared spectroscopy (FTIR) indicated that there was no significant interaction between the HBEO and gelatin. Under storage conditions at 60 °C for 49 days equivalent to 25 °C for 18 months, small decreases in the HBEO retention rate and the antioxidant activity were observed. Thus, the microencapsulated formulation has potential to be applied to other volatile compounds.