Purpose: To report the clinical course, treatment response, and prognosis of Stenotrophomonas maltophilia endophthalmitis following cataract extraction. Methods: The clinical records of six cases of S. maltophilia endophthalmitis after cataract extraction were retrospectively reviewed. Data were collected for surgical characteristics, disease course, culture growth, antibiotic sensitivity of the pathogen, response to treatment, and final visual acuity. Results: Four patients underwent uncomplicated cataract extraction with phacoemulsification (PHACO) and intracapsular intraocular lens (IOL) implantation. One case was complicated by inadvertent posterior capsular tear during PHACO and IOL implantation. One patient underwent a combined extracapsular cataract extraction (ECCE) with IOL implantation and trabeculectomy, but vitrectomy was also performed because of cortical material loss into the vitreous cavity after a capsular tear. Symptoms began between postoperative days 1 and 19. All patients underwent a vitreous tap and intravitreal injections of antibiotics. Medical therapy alone was sufficient in five patients to treat the infection. One patient had four episodes of recurrence. Pars plana vitrectomy with subsequent capsulectomy and IOL extraction were performed in this patient to complete remission. Conclusion: S. maltophilia should be considered a pathogenic organism possibly causing endophthalmitis after PHACO+IOL implantation. The clinical picture resembles acute bacterial endophthalmitis. When the pathogen has settled in the capsular bag, the infection may persist and become refractory to medical treatment.