© 2018 Elsevier HS Journals, Inc. Purpose We assessed the evidence for the use of α2-adrenergic agonists (A2AAs) in bleeding control and field quality in endoscopic sinus surgery. Methods We systematically reviewed randomized clinical trials (RCTs) assessing A2AAs in endoscopic sinus surgery. Abstracts were reviewed by 2 investigators for eligibility, and selected articles were fully reviewed. Data on study design, population, A2AA drug and control groups, bleeding and surgical field quality outcomes, and adverse effects were extracted and synthesized. Findings A total of 13 RCTs that included 896 individuals (7 double-blind trials, 5 single-blind trials, and 1 open-label trial) were selected that assessed the efficacy of clonidine (6 RCTs, 407 patients), dexmedetomidine (6 RCT, 423 patients), or both (1 RCT, 66 patients). Clonidine was compared with placebo (3 RCTs), midazolam (1 RCT), and remifentanil (2 RCTs). Dexmedetomidine was compared with esmolol (2 RCTs), remifentanil (2 RCTs), nitroglycerin and esmolol (1 RCT), and magnesium sulfate (1 RCT). Clonidine and dexmedetomidine were compared in 1 RCT. Clonidine reduced the proportion of individuals with an impaired surgical field by 23% vs placebo (number needed to treat = 4). Clonidine was better than midazolam and remifentanil in 2 trials, and dexmedetomidine was better than magnesium sulfate and esmolol in 2 trials but was not superior to esmolol, remifentanil, or nitroglycerin in 4 trials. Dexmedetomidine produced significantly better differences in bleeding outcomes versus clonidine. Adverse events were infrequent and mainly caused by hypotension or bradycardia. Implications RCTs consistently report that A2AAs reduce bleeding and improve surgical field quality during endoscopic sinus surgery. Adverse event reporting was often omitted in RCTs. Well-designed RCTs with appropriate sample sizes are desirable to identify the best A2AAs and confirm their potential effects on clinical outcomes.