Abstract: A fiber optic adapter includes an outer housing, a receiving seat, and a blocking mechanism. The outer housing defines two connection slots. The receiving seat is connected detachably to the outer housing, and defines two through grooves respectively in spatial communication with the connection slots. The blocking mechanism includes a pivot shaft, a torsion spring sleeved on the pivot shaft, and two cover plates connected pivotally to the pivot shaft and respectively connected to two opposite ends of the torsion spring. When each cover plate is in a blocking position, the cover plate blocks a respective connection slot, and is inclined relative to a central axis of the respective connection slot with a free end thereof being more towards the rear than the pivot shaft, and with an angle that is defines between the cover plate and the central axis being not a right angle.