The present disclosure provides a portable electronic device and an optical proximity sensor module thereof. The optical proximity sensor module includes a circuit substrate, a light-emitting element, an optical proximity sensor element, a light-transmitting package structure and a light-shielding structure. The light-emitting element and the optical proximity sensor element are disposed on the circuit substrate. The light-transmitting package structure includes a first package body disposed on the circuit substrate to enclose the light-emitting element and a second package body disposed on the circuit substrate to enclose the optical proximity sensor element. The light-shielding structure is disposed on the light-transmitting package structure to enclose one part of the first package body and one part of the second package body. The second package body has a second exposed surface exposed from the light-shielding structure, and the second exposed surface has an inclined surface disposed above the optical proximity sensor element.