The Be star 59 Cyg was directly confirmed to be an evolved Be binary with a sdO companion (Be + sdO) by a weak HeII 4686 absorption. Orbital elements and stellar masses were determined. The orbital period was found to be 28.192 ± 0.004 d with a slightly eccentric orbit of e = 0.11 ± 0.005. The mass of the secondary is located in the range between 1.56 and 2.3 M Ø. Thus, 59 Cyg most likely resembles the well known Be + sdO binary φ Per in an earlier stage. Characteristic features for Be binaries with sdO or white dwarf companions were identified. They can be used for an easier identification of further evolved Be binaries or candidate systems.