Influence of oxygen deficiency and salt stresses on survival, biomass growth, photosynthetic rate, and sugar contents were examined using seedlings of two mangroves species, Avicennia marina and Kandelia obovata collected in Okinawa City, Okinawa Prefecture, Japan. When compared the 4 treatments (hypoxia treatment, salt treatment, hypoxia/salt complex treatment, and control treatment), survival rates and biomass of both tree species were reduced remarkably in salt treatment. Photosynthetic rate of A. marina tended to recover after 3 weeks from the salt treatment. The photosynthetic rate of K. obovata was lowered at 4 weeks after the treatment even in the hypoxia treatment. The soluble saccharide content of A. marina was not significantly affected by any treatment, while the content in leaf and roots of K. obovata was increased in salt treatments. From this experiment, it was suggested that both species showed different responses in hypoxia/salt complex treatment compared to each of hypoxia and salt treatments.