This study aimed to determine the Gas Chrommatography (GC)-Mass Spectrometry (MS) profiles and insecticidal activity of essential oils (EOs) from Thymus vulgaris (Thyme) and Cymbopogon citratus (Lemongrass) against the invasive and devastating pest, Tuta absoluta (T. absoluta) through contact and fumigation routes. We found out that thyme oil was predominantly constituted of Thymol (22.16%), α-Pinene (15.35%) and p-Cymene (13.54%) whilst Neral (21.41%), Geranial (21.36%) and β-Myrcene (9.74%) were the major constituents of lemongrass oil. Lemongrass oil exhibited higher insecticidal efficiency irrespective of application mode with 50% lethal dose (LD50) values of 35.8 and 72.2 µL.L-1air on contact and fumigation routes, respectively. Lemongrass oil also lengthened pupal duration at all tested doses irrespective of application routes. The overall responses of Lemongrass oil surpassed that of the reference insecticide (Lynx®: Lambda-cyhalothrine; Acetamipride). Thus, the recorded data clearly showed the acute and long-term insecticidal effects of the studied EOs, though a greenhouse and open field trials are required prior to the validation of this approach as remediation measure for Integrated Pest Management (IPM) for tomato borer control in Cameroon and elsewhere.