We present a patient with residual Descemet's membrane diagnosed by anterior segment optical coherence tomography (AS-OCT) after Descemet's stripping endothelial keratoplasty (DSEK). Postoperatively, persistent partial corneal edema and interface fluid without dislocation of the donor button were observed. No improvement of interface fluid was found during the follow-up period. A primary donor graft failure was diagnosed within 4 months, and the patient was regrafted with penetrating keratoplasty. Pathology examination of the specimen revealed the presence of residual Descemet's membrane in the recipient corneal button, confirmed using AS-OCT imaging. This case report demonstrates that inadequate Descemet's stripping in the recipient button could be a potential cause of DSEK failure; AS-OCT is a useful and noninvasive instrument for diagnosing and monitoring this post-DSEK complication.