Significant morbidity in cystic fibrosis (CF) results from chronic lung inflammation, most commonly due to Pseudomonas aeruginosa infection. Recent data suggest that IL-17 contributes to pathological inflammation in the setting of abnormal mucosal immunity, and type 17 immunity–driven inflammatory responses may represent a target to block aberrant inflammation in CF. Indeed, transcriptomic analysis of the airway epithelium from CF patients undergoing clinical bronchoscopy revealed upregulation of IL-17 downstream signature genes, implicating a substantial contribution of IL-17–mediated immunity in CF lungs. Bromodomain and extraterminal domain (BET) chromatin modulators can regulate T cell responses, specifically Th17-mediated inflammation, by mechanisms that include bromodomain-dependent inhibition of acetylated histones at the IL17 locus. Here, we show that, in vitro, BET inhibition potently suppressed Th17 cell responses in explanted CF tissue and inhibited IL-17–driven chemokine production in human bronchial epithelial cells. In an acute P. aeruginosa lung infection murine model, BET inhibition decreased inflammation, without exacerbating infection, suggesting that BET inhibition may be a potential therapeutic target in patients with CF.