The present invention is directed to an allograft intervertebral implant sized and configured for insertion between adjacent vertebral bodies in a spinal fusion surgery. The implant is preferably manufactured from two or more pieces of allograft bone joined together by a joint, more preferably a dovetail joint. The dovetail joint being sized and configured to substantially follow the exterior shape or surface (e.g. perimeter) of the intervertebral implant. The intervertebral implant may also include one or more bone pins for joining the allograft pieces, the pins being inserted into the implant at an angle substantially perpendicular with respect to the dovetail joint. The intervertebral implant may also include one or more through-bores for receiving ostegenic or bone graft material. The intervertebral implant is preferably sized and configured for insertion during a T-PLIF or PLIF procedure.