The Tuzla Peninsula is the most important outcrop area of the Devonian units in Istanbul, NW Turkiye. The diverse conodont and silicified ostracod fauna come from the section MT, located in the southwestern end of the Tuzla Peninsula. Microfaunal studies (conodonts and ostracoda) indicate that the marine Devonian from this section is Givetian in age. It includes the uppermost Tuzla and lower Yorukali members of the Denizli Koyu Formation. The hermanni Zone and disparilis Zone of the late Givetian established on conodonts are recognized at the MT section. Eighteen ostracode species belonging to 17 genera, included in two orders (Palaeocopida and Podocopida) and 12 conodont species are reported from the MT section. The ostracod fauna represents ‘mixed fauna’ composed of thick-shelled taxa that are common in the Eifelian Mega-Assemblage and others spinose and thin-shelled spinose taxa that are common in a Thuringian Mega-Assemblage. The Givetian ostracod records from the ?stanbul Zone correlate with the southern Laurussia and northern Gondwana Devonian ostracod assemblages.