The appropriate surgical technique for the treatment of unstable osteochondral lesions of the knee remains unclear and had been traditionally described with an open arthrotomy. Administration of bone grafting material in the knee may be performed for a variety of pathologic conditions, including unstable osteochondritis dissecans, traumatic osteochondral defects, or subchondral fracture nonunion, or for preparation of residual tunnels during revision anterior cruciate ligament reconstruction. Although various grafting materials have been described in the literature, cancellous autograft remains the gold standard for treatment safety and efficacy. We describe a successful technique for arthroscopic delivery of autogenous bone graft during fixation of unstable osteochondral lesions of the knee. When the indication for grafting is established, cancellous autograft is harvested from the proximal tibia, undergoes morcellation, and is soaked in bone marrow aspirate obtained through the harvest window. The bone graft is then packed into a modified tuberculin syringe. After arthroscopic preparation of the unstable osteochondral fragment and the respective donor surface, the tuberculin syringe is placed through a standard arthroscopy portal and the bone graft is introduced into the defect under direct visualization, followed by an appropriate osteochondral fixation technique.