Tarhana is a popular traditional Turkish cereal based fermented and functional food mainly produced at home or at home-scale level. It is prepared by mixing wheat flour, yoghurt, yeast, salt, some raw or cooked vegetables (tomato, pepper and onion) and spices (mint, basil, dill, paprika, tarhana herb etc.) followed by lactic and alcoholic fermentation for one to seven days. Tarhana is mainly used in the form of a thick and creamy soup reconstituting with water followed by simmering and is consumed at lunch or dinner especially on cold days in Turkey. Tarhana-like products are known under different names in the other countries: kishk (sour milk-wheat mixture with boiled chicken stock) in Egypt, Syria, Lebonon and Jordan, kushuk (milk-sour dough mixture with turnips) in Iraq, and tahonya/ talkuna (fermented cereal mixture with vegetables) in Hungary and Finland. The low pH (3.8-4.5) and low moisture content (about 10%) of tarhana provide a bacteriostatic effect against pathogenic and spoilage microorganisms. However, some certain mould species can grow even at low moisture and pH values and produce mycotoxins in several food commodities. Among all mycotoxins, Ochratoxin A, is a well-known nephrotoxic, hepatotoxic, teratogenic and carcinogenic mycotoxin, produced by some species of mould genera such as Aspergillus spp. (mainly A. ochraceus) and Penicillium spp. (mainly P. verrucosum) under various environmental conditions. This study was conducted to determine Ochratoxin A levels in tarhana. For this purpose a total of 75 tarhana powder samples were collected from bazaars and markets in Istanbul and analysed for Ochratoxin A by means of LC-MS/MS. As a result, 14 out of 75 tarhana samples (18.7%) were found to be contaminated with Ochratoxin A in the range of 0.052 – 3.62 μg/kg. Only one of the examined samples exceeded the maximum limits of Ochratoxin A (3 μg/kg) set in the Turkish Food Codex. The average pH, moisture and aw results were detected as 3.72, 13.25% and 0.705, respectively.