This study aimed to develop a headspace GC-FID method for the analysis of terpinen-4-ol in Zingiber montanum (Plai) essential oil. The volatile oil was extracted from fresh Z. montanum rhizomes by steam distillation. The amount of terpinen-4-ol was determined by a headspace gas chromatography-flame ionization detector (HS GC-FID) method using benzyl alcohol as an internal standard. The developed method was validated according to the parameters recommended by the International Conference on Harmonization (ICH). Linearity was accessed across the concentration range of 2.5 – 15 µL/mL. The plot of the peak area ratio versus the concentration provided a good linear of this method with a correlation coefficient (r²) of 0.9989. The LOD and LOQ were found to be 0.20 and 2.5 µg/mL, respectively, which indicated a high sensitivity of the method. The instrument (n = 6), intra-day (n = 9), and inter-day (n = 3) precision as indicated by %RSD were 1.77, 1.73, and 1.77 %, respectively. The recoveries at 3 different levels of terpinen-4-ol were between 100.23 to 100.85%. The content of terpinen-4-ol in Plai essential oil was 15.53 ± 0.27 % v/v. The developed method can be used in routine analysis of Plai essential oil and its products in both cosmetic and pharmaceutical industries.