This systematic review (SR) describes the efficacy and safety of biologic disease modifying anti-rheumatic drugs (bDMARDs) for patients with adult-onset Still's disease (AOSD). Three randomised controlled trials (RCTs), one retrospective case series of multiple interventions, and 17 case series of single interventions met the inclusion criteria for this SR. Comparisons of biologic therapy in AOSD were only available against conventional DMARDs in one RCT and against placebo in two RCTs. There was a lack of common assessment criteria, meaning treatment efficacy across studies could not be compared. Uncontrolled retrospective case series suggested that bDMARDs have an effect for patients with AOSD, but these studies did not provide comparative data to show whether bDMARDs were more effective than other interventions or, whether any bDMARD was more effective than another bDMARD. However, there was evidence that bDMARDs could reduce steroid dose. Safety data from all included studies showed that bDMARDs appear to be a safe alternative to conventional DMARDs. This SR has highlighted the need for larger comparative studies in AOSD and has shown the need to standardize the definition of therapeutic response in AOSD. This would allow comparisons between studies in order to gain clarity on which bDMARDs may be more effective treatments for AOSD.