BACKGROUND Assessing implanted biological reinforcement graft success in soft-tissue repairs is typically limited to noninvasive measurements and functional outcome measures. However, there are times when a histologic snapshot of the graft incorporation may be possible owing to a nongraft-related postoperative complication, such as hardware failure. METHODS We histologically evaluated a 6-month biopsy sample from an Achilles tendon repair augmented with an acellular human dermal matrix (AHDM). A 57-year-old woman was treated for Haglund's deformity of the Achilles tendon. The Achilles tendon was fixed to the calcaneus using a plate, and an AHDM was used to augment the primary repair of the tendon. At 6 months, the hardware was removed owing to prominence, and a biopsy of the AHDM was performed. The specimen was prepared and stained using hematoxylin and eosin, Verhoeff-van Gieson, Movat's pentachrome, and toluidine blue stains. RESULTS Visually, the graft appeared normal and incorporated with the native tendon. No repeated tear was observed, and results of tests for infection were negative. Histologically, the graft was infiltrated predominantly with fibroblasts and demonstrated numerous blood vessels. Positive proteoglycan staining in the AHDM and at sites of vascularity indicated probable transformation to tendon-like tissue. CONCLUSIONS These histologic findings suggest that the AHDM is highly biocompatible, supports revascularization and repopulation with noninflammatory host cells, and becomes incorporated by surrounding tendon tissue.