Rationale: We recently demonstrated that the triple combination CFTR modulator therapy elexacaftor/tezacaftor/ivacaftor (ELX/TEZ/IVA) improves lung ventilation and airway mucus plugging determined by multiple-breath washout and magnetic resonance imaging in CF patients with at least one F508del allele. However, effects of ELX/TEZ/IVA on viscoelastic properties of airway mucus, chronic airway infection and inflammation have not been studied. Objectives: To examine the effects of ELX/TEZ/IVA on airway mucus rheology, microbiome and inflammation in CF patients with one or two F508del alleles aged 12 years and older. Methods: In this prospective observational study, we determined sputum rheology, microbiome, inflammation markers and proteome before and 1, 3 and 12 months after initiation of ELX/TEZ/IVA. Measurements and Main Results: CF patients with at least one F508del allele and healthy controls were enrolled in this study. ELX/TEZ/IVA improved the elastic and viscous modulus of CF sputum. Further, ELX/TEZ/IVA improved the microbiome α-diversity and decreased the relative abundance of Pseudomonas aeruginosa (P<0.05) in CF sputum. ELX/TEZ/IVA also reduced IL-8 and free NE activity, and shifted the CF sputum proteome towards healthy. Conclusions: Our data demonstrate that ELX/TEZ/IVA improves sputum viscoelastic properties, chronic airway infection and inflammation in CF patients with at least one F508del allele, however, without reaching levels close to healthy.