Systems for and methods of fusing a sacroiliac joint are provided which include an implant assembly adapted to be inserted into the joint space defined by the bones of a sacrum and an ilium, a delivery tool and means for inserting the implant assembly into the joint. The implant assembly includes a body disposed intermediate distal and proximate end portions thereof and having oppositely disposed side members adapted to expandably engage the sacroiliac joint following insertion of the assembly into the joint space. A tool is provided and provides a means for placing the implant assembly adjacent the sacroiliac joint, inserting it into the joint space and expanding means are thereafter applied to expand the oppositely disposed side members into operative engagement with the joint.