In order to determine the phytoplankton species of southwestern coast of the Black Sea, and the environmental factors that affect the distributions of the species, the water samples were collected vertically and horizontally with a plankton net at different depths at 5 stations between December 2012-November 2013. From the examination of the samples, 83 phytoplankton species belonging to 4 classes were identified. The majority of the species composition was represented by dinoflagellates (56%) and diatoms (41%) respectively. The highest cell numbers of phytoplankton were recorded in December (28730 cell/L) and August (35490 cell/L) in this study. Primary ecological variables, such as temperature (7.97-26.17 degrees C), salinity (13.58-17.75 parts per thousand), dissolved oxygen (3.63-16.65 mg/L) and pH (4.8-9.94), were recorded on each sampling occasion. In addition, nitrite+nitrate-N (0.01-3.24 mu g-at N/L), ammonium-N (0.01-16.5 mu g-at N/L), phosphate-P (0.01-6.47 mu g-at P/L) and silicate-Si (0.71-72.42 mu g-at Si/L) concentrations were measured, and also chlorophyll-a and suspended solid material values ranged between 0.05-3.31 mu g/L and 0.007-0.042 g/L, respectively. Spearman's rank correlation analysis was used to determine the relation between phytoplankton species and ecological variables, and Bray-Curtis analysis was applied to bring out the similarity between stations. The percentage of the similarity was 85% between stations.