This paper describes the activity against Anisakis simplex s.l. L 3 larvae of six monoterpenic derivatives obtained from different essential oils, (α-pinene, β-pinene, ocimene, myrcene, geranyl acetate, and cineole). In in vitro assays, α-pinene, ocimene and cineole showed high activity at a concentration of 125μg/mL (48h) but only α-pinene and ocimene were active at 62.5μg/mL. In in vivo assays, L 3 larvae and study compounds were simultaneously administered per os to Wistar rats. The most active compound was α-pinene, finding lesions in only 20% of treated rats versus 98% of controls. Further in vivo studies are required to investigate whether addition of these compounds to food could have a prophylactic effect, reducing the pathogenicity of A. simplex s.l. L 3 in humans, and to explore any possible synergy among compounds.