Trinajstići is located in the City of Kastav, in Primorje-Gorski Kotar County at an elevation of 290 meters above sea level and it covers the area of 0.21 km² (0.08 sq. miles). Nobody lives in Trinajstićima anymore. but also Serbs (5%) and Bosniaks (4%). Nearby places: Spinčići, Jušići, Matulji, Rubeši, Jurdani, Kastav, Ćikovići, Mihotići, Pobri and Rukavac.