A foam affixing mechanism employed to affix foam to a workpiece, includes a robot arm, a foam supplying assembly and a clamping assembly. The foam supplying assembly is located adjacent to the robot arm to supply foam pieces. The clamping assembly is mounted on the robot arm. The clamping assembly includes a fixing frame, a driving member, a pair of fixing members, and a pair of clamping subassemblies. The driving member is mounted on the fixing frame, the pair of fixing members are fixed to the fixing frame. The clamping subassembly includes a first linking member rotatably connected to the driving member and a second linking member rotatably connected to the first linking member. The second linking member is rotatably connected to the fixing member by a middle portion thereof, the second linking member includes a clamping portion at an end. The present invention further discloses a clamping assembly.