In a continuing search for novel bioactive compounds from marine mangrove plants, seven new naphthoquinone derivatives were isolated from Avicennia marina, namely, avicennone A (1), avicennone B (2), avicennone C (3), avicennone D (4), avicenone E (5), avicennone F (6), and avicennone G (7), along with the known compounds avicequinone A (8), stenocarpoquinone B (9), avicequinone C (10), avicenol A (11), and avicenol C (12). The chemical structures of 1−7 were elucidated by spectroscopic methods. Compounds 8−10, and a mixture of 4 and 5, which all contain a 4,9-dione group, showed strong antiproliferative and moderate cytotoxic activities, as well as antibacterial effects.