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Background: The placebo effect observed in clinical trials evaluating medical treatments for chronic rhinosinusitis (CRS) is not well understood. This systematic review and meta‐analysis sought to characterize the placebo effect present within CRS outcomes. Methods: A systematic review of PubMed, Scopus, and Cumulated Index in Nursing and Allied Health Nursing (CINAHL) was performed. Randomized controlled trials (RCTs) evaluating medical treatments for CRS versus placebo were included. We assessed patient‐reported (sino‐nasal outcome test 22 [SNOT‐22], nasal obstruction, sense of smell, nasal obstruction visual analogue score [VAS], sense of smell VAS, anterior rhinorrhea, and postnasal drip) and objective (Lund–Mackay Computed tomography (CT) score, peak nasal inspiratory flow [PNIF], nasal polyp scores, 40‐item Smell Identification Test, serum IgE, and blood eosinophil levels) outcomes. Results: Twenty‐one RCTs were included, comprising 1437 patients (mean age 49.2 years). Biologics were the most common treatment investigated (n = 9). Eleven studies administered background steroids along with placebo. Following placebo administration, multiple patient‐reported outcomes significantly decreased, including SNOT‐22 (mean difference −9.49, 95% confidence interval [CI] [−11.26, −7.73]), nasal obstruction (−0.33 [−0.54, −0.13]), sense of smell (−0.22 [−0.33, −0.11]), nasal obstruction VAS (−2.47 [−2.87, −2.06]), and loss of smell VAS (−2.31 [−4.14, −0.47]) scores. For objective measures, significant changes occurred in Lund–Mackay CT score (−0.82, [−1.48, −0.16]) and PNIF (4.70, [4.76, 24.64]) with placebo. Placebo arms had the greatest impact when no background medications were used. Conclusions: Placebo treatments have a statistically and potentially clinically significant effect on patient‐reported and some objective CRS outcomes. Further investigation is required to fully understand placebo effect, which could improve assessment of RCTs and impact patient care. [ABSTRACT FROM AUTHOR]