Purpose: To report the first case of fulminant Serratia marcescens panophthalmitis after penetrating keratoplasty (PK). Methods: This is a report of a patient who developed fulminant panophthalmitis shortly after undergoing PK with anterior chamber intraocular lens placement. Slit-lamp examination, B-scan ultrasound (B scan), and orbital computed tomography of the left eye (OS) were performed to further evaluate the patient. Tissue culture and histopathologic examination of the corneal specimen were completed to confirm the diagnosis. Results: A 78-year-old pseudophakic woman presented with 2 days of increasing pain, swelling, and purulent discharge after uneventful PK and secondary anterior chamber intraocular lens placement OS. Examination was notable for light perception without projection, elevated intraocular pressure of 48 mmHg, and a perforated corneal ulcer. B scan demonstrated diffuse vitreous opacities and membranes. Orbital computed tomography demonstrated proptosis and high-attenuation material within the left globe. Canthotomy, vitreous sampling, and antibiotic injections were performed. Corneal tissue cultures grew S. marcescens. Therapeutic PK was performed, but after rapid decompensation, the eye was eviscerated. Conclusions: This is the only reported case of fulminant S. marcescens panophthalmitis after PK. S. marcescens panophthalmitis is an aggressive and rapidly progressive infection with poor visual outcomes despite appropriate intravitreal and systemic antibiotic therapy.