Studies on sea turtles in Turkey have mostly been concentrated on nesting beaches. Although there is no sea turtle nesting beaches on the northern Aegean Sea coast, there are stranded sea turtle records from the northern Aegean Sea and the Sea of Marmara. This study aimed to investigate causes of strandings and their spatio-temporal distribution in these two seas between 2010 and 2017. For data acquisition, denunciations to the Canakkale Onsekiz Mart University's Sea Turtle Research and Application Center (COMU-DEKUM) were used. A total of 37 sea turtles were studied; 8.1% of them were Chelonia mydas, and 91.9% were Caretta caretta. The number of dead strandings (53%) was higher than that of injured strandings (47%). The mean curved carapace length and width of the 27 C. caretta individuals were 68.97 cm and 61.96 cm, respectively, and for C. mydas, these values were 34.5 cm and 29.5 cm, respectively. The most intensive area of strandings was Canakkale (76.5%). Moreover, although adult sea turtles were frequently stranded in the Sea of Marmara, sub-adult sea turtles were frequently stranded in the northern Aegean Sea. The leading causes of strandings in the study site were identified as intentional harm (45.9%) and fishing activities (27%). The results of this study show that coasts of the northern Aegean and the Sea of Marmara may be marine habitats of sea turtles. It is recommended that awareness-raising activities for fishermen in the region should be initiated. (C) 2018 Elsevier B.V. All rights reserved.