© 2020 by the American Thoracic Society. Rationale: Modulation of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) protein improves clinical outcomes in patients with CF and specific CFTR genetic mutations. It remains unclear how improving CFTR function modifies existing airway infection and inflammation. Objectives: To compare sputum microbiome and markers of inflammation before and after 6 months of ivacaftor treatment. Methods: The study included 31 people with CF, ages 10 years and older, with at least one G551D CFTR allele and an forced expiratory volume in 1 second (FEV1) of 40% predicted or greater who were enrolled in the GOAL (G551D Observational) study. Sputum samples were collected either by induction (n = 14) or by spontaneous expectoration (n = 17) before and 6 months after initiation of ivacaftor. Changes in bacterial community indices by sequencing of 16S rRNA amplicons, total and specific bacterial load, and a panel of proteases, antiproteases, and inflammatory cytokines were determined. Results: The cohort that spontaneously expectorated sputum had a lower FEV1, a higher proportion with Pseudomonas aeruginosa infection, and higher concentrations of sputum inflammatory markers compared with the cohort that provided sputum by induction. Although the overall cohort experienced significant improvements in FEV1 and reductions in sweat chloride, no significant changes in bacterial diversity, specific bacterial pathogens, or markers of inflammation were observed in these subjects. Neither total bacterial load nor presence of Pseudomonas changed significantly between paired samples with ivacaftor treatment. Younger patients experienced more shifts in their microbial communities than older patients. Conclusions: In this multicenter cohort, 6 months of ivacaftor treatment were not associated with significant changes in airway microbial communities or measures of inflammation. These data suggest that concomitant antimicrobial and antiinflammatory treatments will still be needed to manage airway disease in patients with CF treated with highly effective CFTR modulator therapy, especially in older patients with more advanced disease.