A distinct type of partial-thickness rotator cuff tear has been observed in overhead athletes, characterized by partial failure of the undersurface of the posterior supraspinatus and anterior infraspinatus tendons with intratendinous delamination. We present a technique of percutaneous intratendinous repair using nonabsorbable mattress sutures designed for the management of articular-side delaminated partial-thickness tears. After tear evaluation and preparation, the torn rotator cuff undersurface is held in a reduced position with a grasper through an anterolateral rotator interval portal while viewing intra-articularly. Two spinal needles are then placed percutaneously through the full thickness of the torn and intact rotator cuff. A polydioxanone suture is passed through each needle, retrieved out the anterior portal, and used to shuttle a single nonabsorbable No. 2 suture through the tissue, creating a mattress suture. Multiple mattress sutures can be placed as dictated by tear size and morphology, with suture retrieval and knot securing then proceeding in the subacromial space. We have adopted this approach with the goals of anatomically re-establishing the rotator cuff insertion and sealing the area of intratendinous delamination while preventing significant alteration to the anatomy of the rotator cuff insertion, which could lead to motion deficits, internal impingement, and potential tear recurrence.