Tea tree oil (TTO) is a volatile essential oil obtained by distillation, mainly from the Australian native plantMelaleuca alternifolia(Maiden & Betche) Cheel (Myrtaceae). In this study, a comparative analysis of the chemical constituents of seven tea tree oils (M. alternifolia) and four otherMelaleucaspp. oils (M. cajuputi, (MCa), two chemotypes ofM. quinquenervia, (MNeand MNi), andM. ericifolia(MRo)) was carried out using gas chromatography–mass spectrometry (GC-MS) and high-performance thin-layer chromatography (HPTLC). Among the seven TTOs, terpinen-4-ol (37.66–44.28%), γ-terpinene (16.42–20.75%), α-terpinene (3.47–12.62%), α-terpineol (3.11–4.66%), and terpinolene (2.75–4.19%) were the most abundant compounds. On the other hand, the most abundant compounds of the otherMelaleucaoils varied, such as 1,8-cineole (64.63%) in MCaoil, (E)-nerolidol (48.40%) and linalool (33.30%) in MNeoil, 1,8-cineole (52.20%) in MNioil, and linalool (38.19%) and 1,8-cineole (27.57%) in MRooil. HPTLC fingerprinting ofMelaleucaoils enabled the discrimination of TTO oils from otherMelaleucaspp. oils. Variation was observed in the profile of the Rfvalues among EOs. The present study shows that HPTLC is one of the best ways to identify and evaluate the quality control in authenticating TTOs, otherMelaleucaEOs, or EOs from other species within the Myrtaceae.