Introduction: A case of ocular bartonellosis under anti-tumour necrosis factor treatment is described. Case description: A 29-year-old woman with psoriasis who had been on certolizumab treatment was examined with a left visual deterioration following a fever bout, malaise, and placoid erythematous rashes on her neck. As there was acute anterior uveitis in her left eye, it was recommended to stop certolizumab treatment for a possible infectious aetiology. However, her physician elected to continue the certolizumab treatment. Ten days later, the patient noticed further visual decline despite the topical steroid treatment. This time, there were scattered yellow-white small retinitis foci at the left posterior pole. Infectious agents were searched and while Discussion: Though extremely rare, ocular bartonellosis should be kept in mind in patients on anti-tumour necrosis factor treatment as rapid and accurate diagnosis may end up with an excellent visual outcome and full recovery. LEARNING POINTS: Anti-tumour necrosis factor treatment is fraught with several ocular side effects including myositis, corneal infiltrates, scleritis, uveitis, optic neuritis, retinal vasculitis and ophthalmoplegia.When a new uveitis episode occurs in cases undergoing anti-tumour necrosis factor therapy, its cause poses a diagnostic challenge as it can have either an infectious or a non-infectious nature.Though very rare, ocular bartonellosis may also occur in immunocompromised individuals and a prompt diagnosis and appropriate treatment can lead to an excellent visual recovery.