Tea tree oil, an active ingredient of skin, hair and nail care cosmeceuticals, has claims for topical antimicrobial, analgesic and anti-inflammatory activity. Its complex composition is governed by ISO 4730:2017. Terpinene-4-ol is the principal constituent of the oil (35% - 48%) followed by γ-terpinene (14% -28%), α-terpinene (6%-12%) and 1,8-cineole (≤15%). A reversed-phase, isocratic high performance liquid chromatographic method has been developed and validated for routine determination of tea tree oil based on1,8-cineole content in bulk and commercially available cosmeceuticals using C18 column, methanol-water (70:30 v/v) as mobile phase and flow rate of 1mL/min. UV detection was done at 200 nm. Linearity of the method was established for 20-100μL/mL (R2 = 0.9992) with LOD, LOQ values of 0.5594 μL/mL and 5.5941μL/mL respectively. The % RSD values for robustness and precision were <1% and recovery ranged between 99.09-102.96%. The method was successfully applied for determination of 1,8-cineole content in cosmeceuticals.