A filamentous green alga Cladophora vadorum (Areschoug) Kützing, bloomed at Shangrok Beach, Buan, Republic of Korea, in September 2015. This alga is currently distributed worldwide. Concentrations of total nitrogen (TN), total phosphorus (TP), dissolved inorganic nitrogen (DIN), and dissolved inorganic phosphorus (DIP) were analyzed in the bloom area and compared to those of other areas in the vicinity. DIN and DIP concentrations were similar to those of other areas. However, TN and TP were as much as six and ten times higher than in other areas, respectively. As in other Cladophora species, the bloom of C. vadorum at Shangrok Beach in 2015 appears to have depended on the TP concentration in the seawater. This suggests that blooms in the area can be controlled by reducing TP.Key words: Bloom, Cladophora vadorum, Total Phosphorus, Total Nitrogen This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial Licens (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.