This study was carried out in western Black Sea Region of Turkey (Bolu, Kastamonu, Karabük, Bartin and Zonguldak) in between 1999 and 2003. The research area is sited in A2 square, which is in grid system adopted by Henderson (1961) as well as in Euro-Siberian phytogeographical region. After the identification of 1840 moss specimens collected from the research area, total 189 taxa were found. They are in the levels of species, subspecies and varieties belonging to 88 genera and 34 families. Among them 28 taxa are new for this grid. Moreover, Pogonatum dentatum (Brid.) Brid., Cynodontium bruntonii (Sm.) Bruch & Schimp., Bryum gemmilucens R.Wilczek & Demaret, Mnium thomsonii Schimp., Ctenidium molluscum (Hedw.) Mitt. var. robustum Boulay., Hyocomium armoricum (Brid.) Wijk & Margad. are recorded for second time only on mainland Turkey.