One of the most important gene centers in Europe is Turkey. But, unfortunately, Turkey has not reached the desired level of production and exportation. In recent years, production has failed to meet walnut demand in the domestic market. Also, walnut exportation has been increasing year by year. In this context, Turkish Government incentives to the private sector for the production of certified walnut saplings gains importance. The purpose of this study is to determine the effect of the tongue grafting methods on the success of grafting in walnut seedlings in three different environmental conditions in Düzce province. These tree different environmental conditions were selected closed tunnel greenhouse, automatic greenhouse and outdoor conditions. Seeds were collected from the wild walnut trees in 2016. Collected walnut seeds were planted to the prepared seedbed located in Düzce Forest Nursery. A total of 15 walnut varieties were used to graft to the two years old wild walnut seedlings. The grafting was carried out on 21-22 April 2018. The grafted materials obtained from 9 native (Yalova1, Yalova3, Yalova4, Şebin, Kaman, Kaplan, Oguzlar, Sapanca and Bilecik) and 6 Nonnative (Fernor, Franquette, Fernette,Pedro, Chandler, Ronde) varieties. The grafting success was counted on 30-31 May 2018. The highest grafting success rate was 82.72% in control greenhouse in walnut varieties, while the lowest success rate was obtained in open fields with 52.12%. The highest grafting successes were Oğuzlar77 (80,92%), Chandler (76,66%), Fernette (72,96%) and Franquette (72,22% 21), Ronde (50,55) and Bilecik (52,59%) varieties, respectively. As a result, the success of walnut grafting can be higher in controlled greenhouse environments.