Amphorellopsis tetragona was reported for the first time from the Sea of Marmara and  contributed to the regional check-list of the plankton species of Turkish seas. The specimen was collected on 17 October 2008 from surface neritic waters with a depth of 30m in the research area. The primary hydrographic parameters, temperature 17 ºC, salinity 27 ppt and dissolved oxygen 5 mg l-1, were recorded at the sampling station.