A mounting unit for a rear suspension is provided. The mounting unit for a rear suspension of a multi link type coupling a rear suspension member to a rear floor side member includes a pipe nut disposed through one side of the rear floor side member and first and second brackets that couple to upper and lower end portions of the pipe nut to the rear floor side member and a rear cross member, respectively. A mounting bolt is coupled to the pipe nut to maintain the position of one side of the rear suspension member to the rear floor side member, and a support bracket is coupled to the rear floor side member and the rear cross member with the first and second brackets through a flange and disposed between an exterior lateral surface of the rear floor side member and a bottom surface of the rear cross member.