This study investigated the viability of phytoplankton from international commercial ships berthed at the Ports of Ulsan and Onsan, Korea to understand the impact of environmental factors on the survival success of introduced species by ship ballast water. Although the number of species and phytoplankton viability in uploaded ballast tanks was not clearly related to the duration time of ballast water, it was dependent on ballasting region. Except for the Royal Diamond from Japan, the nutrient concentration of ship ballast water that arrived from primarily Asian countries was relatively higher than ship side port water. Also, even though phytoplankton viability in the ballast water treatment on the Royal Diamond was not observed due to lower nitrogen and phosphorus sources, re-growth availability of ballast water treatments in other vessels was relatively high. For the irradiance grade experiments on three vessels, phytoplankton growth increased with increasing irradiance. However, the phytoplankton did not respond in continuous dark conditions even with the addition of high nutrients. The Daewoo Diamond introduced several freshwater species from the Changjiang River, China that were adapted to salinities of ten to zero. Nevertheless, the centric diatom Thalassiosira pseudonana was able to tolerate a wide range of salinities (0 to 30) and its species-specific viability was suitable for colonization. The laboratory design of this study can be applied as a practical tool to assess the survival possibility of foreign phytoplankton introduced into local waters.