This paper proposes a sensorless predictive speed control (PSC) technique for permanent-magnet synchronous generators (PMSGs) in variable-speed wind turbines. The proposed technique allows to manipulate all the mechanical and electrical variables (i.e. speed and current/torque) in a single control law to generate the optimal switching state to apply in the next sampling instant. Accordingly, the cascaded-control structure is eliminated, which significantly enhanced the dynamic performance of the proposed control strategy. Furthermore, a non-linear observer is proposed to estimate the speed/position of the rotor and the load torque, and accordingly, the system reliability is enhanced and the cost is reduced. Experimental results using a dSPACE DS1007 R&D controller board-based real time system and14.5 kW PMSG are presented to verify the feasibility of the proposed control algorithm.