Endophthalmitis following cataract surgery is one of the most feared complications, and can have significant impact on the visual outcomes of patients. The role of steroids in the management of endopthalmitis is controversial. The aim of this paper was to determine whether intravitreal dexamethasone as an adjuvant to intravitreal antibiotics is beneficial in the treatment of suspected bacterial endophthalmitis after cataract surgery. This is a randomised, placebo‐controlled superiority trial in three tertiary referral centres in the Netherlands. Patients with suspected bacterial endophthalmitis within six weeks after cataract surgery were eligible. A diagnostic vitreous biopsy was taken for culture, and patients received intravitreal injections of 400μg dexamethasone (without preservatives) or placebo, in addition to 0.2mg vancomycin and 0.05mg gentamicin. The vancomycin and dexamethasone or placebo injections were repeated once at day three or four. Primary outcome measure was best‐corrected visual acuity (BCVA) at one year. Over 10 years a total of 167 patients (81 dexamethasone, 86 placebo) were available for the intention‐to‐treat analysis. Biopsies of 114 patients (68%) were culture‐positive. Final BCVA did not differ between the dexamethasone and the placebo group (logMAR 0.31±0.58 versus 0.27±0.50; p=0.90), nor did the number of patients with final vision of no light perception (LP, 7 versus 13). This study concluded that intravitreal dexamethasone without preservatives as an adjuvant to intravitreal antibiotics does not improve visual acuity (VA) in patients treated for suspected bacterial endophthalmitis after cataract surgery.