We reported a case of 70-year-old man who presented with whitish discoloration of left eye over the past 2 years. Visual acuity in the right eye is 6/18 and is perception and projection of light inaccurate in the left eye. His history includes penetrating keratoplasty (PK) in the right eye for Mooren ulcer. Postoperatively, there were signs of graft rejection, including epithelial sloughing and stromal infiltration, consistent with immunological graft failure. Anterior segment examination revealed total leukomatous corneal opacity in the left eye and superficial vascularization involving 2 quadrants. Following the triple procedure, the patient demonstrated resolution of graft rejection and restoration of corneal clarity. Visual acuity improved significantly, with no signs of recurrent graft rejection during follow-up. Immunological graft failure in Mooren ulcer represents a formidable challenge, often requiring a multimodal approach for successful management. Our case underscores the importance of early recognition and tailored surgical intervention in optimizing outcomes for patients with Mooren ulcer-associated graft failure.