This paper proposes a current-sensorless maximum power point tracking (MPPT) quasi-double-boost converter for photovoltaic (PV) systems. Instead of using sensors, the output current of the PV system is obtained from the measured voltage ripple in the input capacitor of the DC-DC converter. The estimated current is used by a hill-climbing (HC) MPPT algorithm to determine the optimal duty ratio for controlling the DC-DC converter. The operating principle, theoretical analysis, and design guidelines of the quasi-double-boost converter are provided in the paper. Simulation studies are carried out in MATLAB Simulink by using real solar radiation data obtained from the National Renewable Energy Laboratory (NREL); results show that the proposed system and control algorithm work effectively for current-sensorless MPPT control of the PV systems. Experimental results for a real PV system are provided to further validate the simulation of the quasi-double boost converter and testify the effectiveness of the current-sensorless MPPT control algorithm.