A bicycle rear derailleur is basically provided with a base member including a frame mounting portion having a mounting opening, and a fastening member extending through the mounting opening of the base member. The fastening member has a first threaded portion and a placement portion adjacent to the first threaded portion. An adjusting member is configured to adjust a position of the bicycle rear derailleur relative to a bicycle. An intermediate member includes a contact portion disposed between the adjusting member and the bicycle. The intermediate member has a second threaded portion configured to threadedly engage with the first threaded portion of the fastening member. The second threaded portion has an innermost diameter that is smaller than the outermost diameter of the first threaded portion. The intermediate member is disposed on the placement portion of the fastening member.