The invention relates to an intervertebral fusion implant for fusing two adjacent vertebrae, comprising an adjustable support body, the base surface and cover surface of which are configured to bear on end plates of the adjacent vertebrae, wherein provision is made for a side bracket, which can be pivoted laterally about a hinge and the base and cover of which have a planar design, and provision is made for an actuator for pivoting out the side bracket into a position (working position) spread from the support body. As a result, the implant has particularly small dimensions and can, after assembly at the envisaged implantation site, be actuated in such a way that it becomes larger and thereby affords a larger support surface for support in the intervertebral space. Thus, even comparatively large-area defects can be treated by minimally invasive surgery.