Postoperative sore throat negatively affects patient satisfaction and recovery. Numerous randomised trials have tested the efficacy of corticosteroids applied to tracheal tubes to prevent postoperative sore throat. We searched PubMed, EMBASE, the Cochrane Central Register of Controlled Trials, Wanfang Database, and the China Academic Journal Network Publishing Database from inception to 7 December 2017. We included randomised controlled trials that assessed the efficacy and safety of corticosteroids applied to tracheal tubes, compared either with non-analgesic controls and analgesic agents, in adults undergoing elective surgery under general anaesthesia. We pooled the data using a random-effects model and assessed the risk of random error by applying trial sequential analysis. Our primary outcomes were postoperative sore throat 24 h after surgery/extubation, and adverse events. The evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) criteria. We included 20 randomised controlled trials involving 2200 patients. Compared with non-analgesic controls, corticosteroids applied to tracheal tubes were associated with a reduced incidence of postoperative sore throat, risk ratio (95%CI) 0.39 (0.32-0.49) (18 trials, 1506 patients). Two randomised trials reported no adverse events. Compared with lidocaine, corticosteroids applied to tracheal tubes were associated with reduced incidence of postoperative sore throat, risk ratio (95%CI) 0.42 (0.35-0.51) (nine trials, 706 patients). Trial sequential analyses suggested the presence of firm evidence that corticosteroids applied to tracheal tubes were superior both to non-analgesic controls and lidocaine, in preventing postoperative sore throat. Evidence for postoperative sore throat for both comparisons was assessed as high quality. Only two trials sought adverse events; none were recorded.