Agomelatine cocrystals comprising agomelatine or N-[2-(7-methoxy-1-naphthyl)ethyl]acetamide and an organic acid having a solid state at room temperature, are new. An independent claim is included for the preparation of cocrystals. ACTIVITY : Tranquilizer; Hypnotic; Neuroprotective; Antidepressant; Cardiovascular-Gen.; Gastrointestinal-Gen.; CNS-Gen.; Muscular-Gen.; Neuroleptic; Anorectic; Analgesic; Anticonvulsant; Antidiabetic; Antiparkinsonian; Nootropic; Dermatological; Antimigraine; Endocrine-Gen.; Contraceptive; Immunomodulator; Cytostatic. MECHANISM OF ACTION : Melatoninergic system receptor agonist; Hydroxytryptamine receptor antagonist.