The use of essential oils as an eco-friendly tool in pest management stems from their natural origin and the presence of bioactive compounds that exhibit pesticidal properties, offering a sustainable alternative to synthetic chemical pesticides. This study explores the toxicity of Lavandula multifida (lavender) essential oil (EO), as a botanical pesticide against two widespread and destructive Noctuidae pests, Spodoptera littoralis (Boisd.) and Agrotis ipsilon (Hufnagel). GC-MS was employed to characterize 23 compounds in the EO, with 1,3,3-trimethyl-2-oxabicyclo [2.2.2] octane (eucalyptol) (39.84%), being the primary component. The leaf dipping technique was utilized to assess the toxicity of the EO to both insects. At 96 hours post-treatment, the LC50 of lavender EO to S. littoralis and A. ipsilon larvae were 2.350 and 2.991 mg/ml, respectively. Concerning its biological effect, both concentrations of the EO (LC15 and LC50) significantly shortened the duration of the larval (to 15.24 and 14.23 days) and pupal (to 11.19 and 10.55 days) stages of S. littoralis. Biochemical assays revealed that the LC50 of lavender EO significantly inhibited α-esterase activity in S. littoralis at 72- and 96 hours post-treatment (0.031 and 0.063 mmol/min/mg), and A. ipsilon at 96 hours post-treatment (0.129 mmol/min/mg protein). Given its significant toxicological, biological, and biochemical effects on S. littoralis, it is suggested that lavender EO could be considered for use in integrated pest management strategies while ensuring its safe application to protect non-target organisms.