In this paper, an efficient online fractional open-circuit voltage (FOCV) maximum power point tracking (MPPT) algorithm based on sliding mode control (SMC) is presented. The proposed method determines the open-circuit voltage by sensing photovoltaic (PV) module voltage, current, and temperature without disconnecting the PV module. In addition, the proposed method utilizes the SMC strategy to track the maximum power and its results are compared with the conventional PI controller. The SMC achieves the high tracking speed with reduced oscillations and steady-state error as compared to the PI controller. Moreover, the advantages of the proposed method include 1) interruption-free output power 2) harness 2.7% more energy in variable irradiance and temperature conditions 3) higher tracking efficiency as compared to the conventional analytical FOCV algorithm. The effectiveness and robustness of the proposed method and SMC are tested at different environmental conditions in the Matlab/Simulink environment using the 245 W Yingli PV panel.