Creseis acicula is a pteropod species, widely distributed in the world’s ocean. The latest report of its bloom was in the Mediterranean Sea in 1990. On June 12, 2020, an unprecedented bloom of C. acicula was observed in Daya Bay, China, that lasted for over a month and caused economic losses. The maximum abundance of C. acicula was up to 5595 ind. m-3, 1000 times the local record high, and 10 times the highest number recorded elsewhere. Higher abundance (≥ 1000 ind. m-3) was found in the warm water of ≥ 30℃ along the southwest shore of Daya Bay. The initiation of the bloom matched a sharp increase of temperature and chlorophyll a and an abrupt decrease of salinity attributed to heavy rainfall that lasted for more than 20 days. Considering rising occurrences of extreme weather due to global change, possibilities of recurrent C. acicula blooms worldwide certainly deserve attention.