DCOIT is an effective antifouling biocide, which presence in the environment and toxicity towards non-target species has been generating great concern. This study evaluated the waterborne toxicity of DCOIT on marine invertebrates (i.e., survival of brine shrimp Artemia sp., larval development of the sea urchin Echinometra lucunter and the mussel Perna perna), as well as DCOIT-spiked-sediment toxicity on the fecundity rate of the copepod Nitrocra sp. And the mortality of the amphipod Tiburonella viscana. The data outcomes were used to calculate environmental hazards and risks, which were compared to their corresponding values obtained from temperate regions. Waterborne toxicity can be summarized as follows: Artemia sp. (LC50-48h = 163 (135-169) μg/L), E. lucunter (EC50-36h = 33.9 (17-65) μg/L), and P. perna (EC50-48h = 8.3 (7-9) μg/L). For whole-sediment toxicity, metrics were calculated for T. viscana (LC50-10d = 0.5 (0.1-2.6) μg/g) and Nitrocra sp, (EC50-10d = 200 (10-480) μg/kg). The DCOIT hazard was assessed for both tropical and non-tropical pelagic organisms. The predicted no-effect concentration (PNEC) for tropical species (0.19 μg/L) was 1.7-fold lower than that for non-tropical organisms (0.34 μg/L). In whole-sediment exposures, DCOIT presented a PNEC of 0.97 μg/kg, and the risk quotients (RQs) were >1 for areas with constant input of DCOIT such as ports ship/boatyards, marinas, and maritime traffic zones of Korea, Japan, Spain, Malaysia, Indonesia, Vietnam, and Brazil. The presented data are important for supporting the establishment of policies and regulations for booster biocides worldwide.