Aims: To describe and compare the causative organisms, clinical features and visual outcomes of endophthalmitis following intravitreal injection (IVI) to endophthalmitis following cataract surgery. Methods: Patient population and setting: A retrospective case series of patients with acute endophthalmitis following either cataract surgery or IVI presenting to a tertiary referral centre - Sydney Eye Hospital - between 2007 and 2010. Main outcome measures: (1) identification of the causative organism; (2) time to presentation; (3) odds of improvement in visual acuity (VA) following treatment; (4) odds of final VA of counting fingers (CF) or less and (5) odds of enucleation. Results: Of the 101 patients in our study, 48 had preceding cataract surgery and 53 had preceding IVI. There was an increased incidence of Streptococcus spp. endophthalmitis in post-IVI cases (24.53% vs 6.25%; OR 5.85; p=0.022). Endophthalmitis following IVI had increased likelihood of a final VA of CF or less (OR=6.0; p<0.01), decreased likelihood of any improvement in acuity following treatment (OR=0.13; p<0.01) and an increased likelihood of presenting within a week of the procedure (OR=3.93; p<0.01). Endophthalmitis caused by Streptococcus spp. was associated with increased likelihood of a final VA of CF or less (OR=10.2; p<0.01), decreased likelihood of any improvement in acuity following treatment (OR=0.06; p<0.01) and increased likelihood of enucleation (OR=17.11; p<0.01). Conclusions: Endophthalmitis following IVI is associated with an increased incidence of Streptococcus spp. infection, earlier presentation and poorer visual outcomes when compared with endophthalmitis following cataract surgery.