The Fukushima accident released short-lived Cs-134 and longer-lived Cs-137 to the ocean. The amount, although substantial, is much less than that produced during the atomic bomb tests 60 yrs ago. Cs-134 and Cs-137 are anthropogenic radionuclides and soluble in seawater, hence, the radioactivity can be used as a tracer for special event or currents. Here we collected Cs-134 and Cs-137 samples in seawaters surrounding Taiwan including the Kuroshio, the northern South China Sea, the Taiwan Strait, and the southern East China Sea from 2018 to 2021. Most surface seawater samples were collected from boats using 20-L tanks, and a few samples were gathered from the shore. Non-surface seawater samples were taken from R/Vs Ocean Researcher I, II, and III with Niskin bottles mounted on a CTD rosette. All samples were determined in the Radian Monitor Center, Atomic Energy Council of Taiwan. Ammonium molybdophosphate (AMP) was used to pre-concentrated Radiocesium. Each 40-L (60-L) sample was counted for 200,000 s (120,000 s) using a high-purity germanium (HPGe) detector with lead shielding. The detection limits of 137Cs was 0.5 Bq m−3. The averaged surface Cs-137 activities was 1.18±0.25 Bq m-3, however, the activities of Cs-134 samples were all under detection limit. Complete data are archived, including sampling date, location, water depth, temperature, salinity, and Cs-137 activity; total sample amount is 577.