This study was carried out to determine the adaptation capability of 7 foreign walnut cultivars and 6 local walnut cultivars and genotypes in a commercial orchard established at 7 x 8 m spacing under Upk (inner Aegean region/Turkey) ecological conditions during the 2016 and 2017 growing seasons. Phenological and pomological characteristics and fruit set on lateral branches of walnut cultivars were investigated. All of the local walnut cultivars, except for Baikal genotype, were earlier leafing than the foreign walnut cultivars. The leafing of walnut cultivars was the earliest in Sebin (27 March-4 April) and Oguzlar-77 (28 March-4 April), and the latest in Cisco (25-29 April) and Balkal (2430 April). For type of blooming, Kaman-1 cultivar was homogamous, Oguzlar-77 and Arslan-1 genotypes were protogynous, and other cultivars were protandrous. The percentage of lateral bud fruitfulness in walnut cultivars varied between 10% (Balkal) and 90% (Pedro). With regard to pomological characteristics of 13 different walnut cultivars and genotypes, nut weights varied between 10.23 g (Oguzlar-77) - 15.28 g (Arslan-1), kernel weights varied between 4.38 g (Pedro) - 8.16 g (Arslan-1), kernel percentages varied between 34.96% (Cisco) 59.70% (Sebin), and shell thicknesses varied between 1.61 mm (Oguzlar-77) - 2.78 mm (Cisco).