Abstract: Plant growth in coastal estuarine riparian zones is vulnerable to combined waterlogging and salt stresses. Previous studies have shown that Syzygium nervosum A. Cunn. ex DC. and Syzygium cumini (L.) Skeels possess strong waterlogging tolerance. However, their tolerance to combined salinity and waterlogging stress is still unclear. In this study, three treatments, including waterlogging, salinity treatment (350 mmol/ L), and combined salinity-waterlogging treatment (175 mmol/L), were used to compare the effects of different stresses on plant growth, physiological and biochemical traits, and ion accumulation in both species. After 24 d of treatment, the three stress treatments resulted in a decrease in the biomass of both species, as well as an increase in reduced glutathione (GSH) content and activities of ascorbate peroxidase (APX) and glutathione reductase (GR). Compared to the control, waterlogging treatment decreased the contents of superoxide anion (O₂⁻) and hydrogen peroxide (H₂O₂) in the leaves of both species, while increasing the potassium ion (K⁺) content and decreasing the K⁺/Na⁺ ratio in the roots. Compared to the control, salinity treatment decreased the O₂⁻ content in the S. cumini seedlings but increased content in the S. nervosum seedlings. In addition, salinity treatment increased the contents of proline, H₂O₂, sodium ion (Na⁺), and chloride ion (Cl⁻) in both species but decreased the K⁺/Na⁺ ratio. Compared to the control, combined salinity-waterlogging treatment increased the contents of O₂⁻, Na⁺, and Cl⁻ in both species but decreased the K⁺/Na⁺ ratio. In addition, compared to the waterlogging treatment, combined salinity-waterlogging treatment decreased biomass accumulation in both species, while increasing the contents of O₂⁻, Na⁺, and Cl⁻. Compared to the S. nervosum seedlings, the S. cumini seedlings exhibited higher biomass accumulation, proline content, GR activity, and K⁺/Na⁺ ratio, and lower levels in H₂O₂, Na⁺, and Cl⁻ under salinity treatment and combined salinity-waterlogging treatment, suggesting that S. cumini seedlings possess stronger tolerance to salinity and combined salinity-waterlogging than S. nervosum. These findings provide theoretic guidance for vegetation restoration and reconstruction in coastal estuarine wetland systems.