The tomato leafminer (Tuta absoluta) is a devastating pest that causes significant economic losses in tomato production. The use of synthetic insecticides to control these pests has led to resistance and health risks. The potential of essential oils (EOs) as biopesticides has attracted research attention owing to their selectivity and low environmental impact. This study aimed to identify the chemical compositions of EOs extracted by steam distillation from Origanum majorana, O. onites, and Juniperus communis using GC–MS, and to assess their toxicity and repellency against T. absoluta larvae using the leaf-dip method. The GC–MS analyses identified over 99% of the EOs constituents. The main compounds of O. majorana (carvacrol 46.61% and α-terpinolene 36.79%) and O. onites (carvacrol 41.05% and linalool 11.38%) were oxygenated monoterpenes, whereas J. communis (α-pinene 82.08% and β-myrcene 3.61%) was rich in hydrocarbon monoterpenes. Results at 1% concentration showed a larval mortality (toxicity) of 100, 88, and 46.9% at 96h post-treatment, with repellency effects of 88, 72, and 60% at 16h after treatment, and LC50 values of 0.20%, 0.53%, and 0.89% (v/v) for O. majorana, O. onites, and J. communis, respectively. The EO of O. majorana and O. onites demonstrated high toxicity and repellency, whereas J. communis exhibited only a moderate effect against T. absoluta larvae in both tests. These findings indicate that O. majorana and O. onites EOs could serve as alternative, eco-friendly bioinsecticides for managing T. absoluta larvae. Future studies could focus on phytotoxicity and formulation development under field and greenhouse conditions for further validation.