A right angle adapter with an auxiliary handle includes a main body, an adjusting sleeve, a retaining member, a spring member and the auxiliary handle. Upon completion of angular adjustment between the auxiliary handle and the main body, and when the auxiliary handle has not pressed against the main body, the polygonal positioning recess of the adjusting sleeve is mounted and engaged with the polygonal positioning portion of the main body, so that the adjusting sleeve and the auxiliary handle are both prevented from rotating with respect to the main body, meaning that all the components are preliminarily positioned. When the auxiliary handle is screwed tight to make the abutting portion press against the driving portion of the main body, the possibility of angular change between the auxiliary handle and the main body is eliminated, thereby ensuring accurate adjustment and making angular adjustment of the auxiliary handle more convenient.