FeCo–MnO nanocomposites were prepared by ball milling mixtures of Fe, Co and Mn, where MnO was obtained from the oxidation of Mn after or during the milling process. The coercivity and squareness of FeCo–MnO nanocomposites increase with increasing milling time. After annealing treatment, the coercivity and squareness increase and exhibit a maximum at 120h milling time. The temperature dependence of the magnetic properties of FeCo–MnO was also studied and there is a distinct boundary at 120K. The exchange-bias field and the coercivity decrease quickly with increasing temperature from 30 to 120K. However, there are no shifted hysteresis loops and the coercivity decreases slightly with increasing temperature from 120K to room temperature. The enhancement of the coercivity and squareness is mainly attributed to the exchange-bias effects and the reduced magnetic interactions between the FeCo particles by the efficient isolation in MnO matrix.