Abstract Background 5-Aminosalicylates [5-ASAs] are the mainstay of treatment for ulcerative colitis [UC]. The optimum preparation, dose, and route of administration for UC remain unclear. We conducted a network meta-analysis to examine this issue. Methods We searched MEDLINE, EMBASE, EMBASE Classic, and the Cochrane central register of controlled trials from inception to December 2020. We included randomised controlled trials [RCTs] comparing oral, topical, or combined oral and topical 5-ASAs, with each other or placebo for induction of remission or prevention of relapse of UC. Results were reported as pooled relative risks [RRs] with 95% confidence intervals [CIs] to summarise effect of each comparison tested, with treatments ranked according to P-score. Results We identified 40 RCTs for induction of remission and 23 for prevention of relapse. Topical mesalazine [P-score 0.99], or oral and topical mesalazine combined [P-score 0.87] ranked first and second for clinical and endoscopic remission combined. Combined therapy ranked first in trials where ≥50% of patients had left-sided/extensive disease, and topical mesalazine first in trials where ≥50% of patients had proctitis/proctosigmoiditis. High-dose [≥3.3 g/day] oral mesalazine ranked third in most analyses, with the most trials and most patients. For relapse of disease activity, combined therapy and high-dose oral mesalazine ranked first and second, with topical mesalazine third. 5-ASAs were safe and well tolerated, regardless of regimen. Conclusions Our results support previous evidence; however, higher doses of oral mesalazine had more evidence for induction of remission than combined therapy and were significantly more efficacious than lower doses. Future RCTs should better establish the role of combined therapy for induction of remission, as well as optimal doses of oral 5-ASAs to prevent relapse.