The crude methanolic extract of the leaves of Avicennia officinalis L. (Family: Avicenniaceae) was evaluated for its diuretic and neuropharmacological activities. Phytochemical analysis of the ethanolic extract of the leaves of A. officinalis indicates the presence of alkaloid, steroid, flavonoid, reducing sugars and gums. The extract of A. officinalis leaves also potentiated the pentobarbital induced sleeping time in mice, and decreased the open field score in open field test, decreased the number of hole crossed from one chamber in the hole cross test and decreased the head dip responses in hole board test. Diuretic activity was proved by the electrolyte loss ratio (Na+/K+ excretion ratio was 1.52 and 1.33 at the doses of 200 and 400 mg/kg respectively) as that of the standard diuretic furosemide (1.35). The obtained results provide a support for the use of this plant in traditional medicine and its further investigation.