© 2019 Elsevier LtdThis research aimed to evaluate the waste product of cold pressed hazelnut oil for the fortification of kefir beverage. Hazelnut cake was processed to a drinkable beverage that is called as hazelnut milk (HM). The effect of hazelnut milk on physicochemical, rheological, structural, bioactive properties, organic acids profiles and viability of kefir microorganisms was evaluated during storage. Fermentation process was also evaluated by watching acidification kinetics and microorganism growth. Addition more than 50% hazelnut milk resulted to prolong incubation time compared to control sample and also slowed the bacteria growth during fermentation. Hazelnut milk showed stimulating effect on the growth of yeasts in kefir samples. Viscosity, consistency index, water holding capacity and exopolysaccharide content of kefir samples enhanced with the usage of hazelnut milk in the production. Hazelnut milk also led to increase in total phenolic compound content and antioxidant capacity in the kefir samples. Using different milk type changed the organic acid profiles of kefir samples. Hazelnut milk caused to reduction in lactic and citric acid contents while led to increase in malic and acetic acid content.