A fan frame assembly includes a first fan frame and a second fan frame. The first fan frame includes a first annular wall part and a plurality of first engagement parts connected to the first annular wall part. The second fan frame includes a second annular wall part and a plurality of second engagement parts connected to the second annular wall part. Each of the first engagement parts has a positioning structure extending along an axial direction of the first annular wall part, and each of the second engagement parts has a positioning structure extending along the axial direction of the first annular wall part. when the first engagement parts and the second engagement parts are respectively engaged with each other, the positioning structures of the second engagement parts are positioned by the positioning structures of the first engagement parts.