Lettuce mosaic virus (LMV) is considered as the most destructive virus disease of lettuce. The presence of LMV was detected and LMV isolates were comprehensively characterized at molecular level in different parts of the world. While LMV infection was reported several times in different regions of Turkey, molecular characterization of LMV isolates lagged behind in Turkey compared to other regions of the world. For this purpose, surveys were carried out in Canakkale, Balikesir and Bursa provinces, and their districts which constitute South Marmara Region of Turkey in 2013-2015 lettuce cultivation seasons. A total of 307 samples were collected from lettuce plants showing symptoms of viral infection similar to LMV. The collected samples were tested with double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) to determine the presence of LMV. As a result of the tests, 35 of the 307 samples were infected with LMV. Out of 35 infected samples, 15 were selected considering the provinces and their districts where they were collected for further characterization. The coat protein (CP) genes of selected isolates were amplified with reverse transcription-polymerase chain reaction (RT-PCR) to determine the sequence variation in the CP gene of Turkish isolates. RT-PCR amplified CP genes of LMV isolates were cloned and sequenced. Similarity rates and phylogenetic relationships of South Marmara Region LMV isolates with each other and world LMV isolates obtained from GenBank databases were determined.