A new approach to enhancing plant activities is encouraged. Fresh leaves of Lippia chevalieri were dried, ground and fractionated into granulometric classes (≤ 212 µm; 212 - 425 µm; ≥ 425 µm) by sieving. The essential oils (EOs) were analyzed by gas chromatography (GC) coupled with mass spectrometry (MS). Antioxidant activity was evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) tests. Larvicidal efficacy was tested on Anopheles gambiae s.l. under laboratory conditions. Particle size had a significant influence (p < 0.05) on the phytocompounds, antioxidant and larvicidal properties of the EOs. Comparatively, the number of phytochemicals decreases as we move towards fine particles. The ≤ 212 µm EO fraction exhibited higher DPPH (IC50 = 78.2 ± 2.24 μg/mL) and FRAP (48.72 ± 0.028 mgAAE/gEO) activities than did ascorbic acid. Fresh leaves, dry leaves, unsieved powder and large particles (≥ 425 µm) induced significant (P < 0.05) concentration-dependent larvicidal activity, with LC50s of 1,93, 1.55, 1.68 and 2.11 mg/mL, respectively. Grinding followed by sieving results in the accumulation of the majority of antioxidant compounds in the EO of fine particles. Drying and grinding increases the larvicidal efficacy of the plant, while fractioning into fine particles progressively reduces the efficacy as a function of particle size.