The aim of this study was to research the morphology and to make ready a hair identification key for common mammals in Turkey and also to make up a comprehensive method for the preparation of hair identification key for Turkey's mammals. Despite the wide application of this technique in the determination of diet composition in large carnivores, it has not been used in Turkey up to this point, thus this paper is the first study and an appropriate guide for using this technique in ecological studies and management of many species and populations in Turkey. In this research, hair structures of eighteen species representing four mammalian orders including Artiodactyla such as wild goat, chamois, red deer; Carnivora such as leopard, eurasian lynx, gray wolf, brown bear; Lagomorpha and Rodentia were investigated. The studied large carnivore species constitute the main predator species and the others are important prey sources. The microscopic structure of the hair was studied using the hair medulla and cuticle scale patterns. Afterwards, the structural features of hair for each species were comparatively used in order to prepare a descriptive and photographic hair identification key.