Two new germacrane sesquiterpenes, including (1Z,4Z)-7alphaH-11-aminogermacra-1(10),4-diene (1) and N,N'-11-bis[(1Z,4Z)-7alphaH-germacra-1(10),4-dienyl]urea (2), were isolated from a Thai marine sponge Axinyssan. sp. collected from the Andaman Sea. The structure elucidations of 1 and 2 were accomplished by means of 1D and 2D NMR, MS, and IR spectroscopy. Only 1 exhibited strong antimicrobial activity against Staphylococcus aureus, Bacillus subtilis, and Candida albicans.