The mental health effects of elexacaftor/tezacaftor/ivacaftor (ETI) on adults with CF are still uncertain with mixed findings from published studies. To systematically investigate the impact of ETI on symptoms of anxiety and depression in adults with CF, Generalized Anxiety Disorder-7 (GAD-7) and Patient Health Questionnaire (PHQ-9) scores were evaluated at baseline, 6 months, and 12 months post-ETI. Overall, GAD-7 and PHQ-9 scores improved at 6 months post-ETI, with a greater proportion of individuals experiencing a clinically significant improvement (vs. worsening) of their symptoms, which was sustained at 12 months. Factors influencing mental health outcomes included pre-existing psychiatric diagnoses and psychiatric medication use. In conclusion, although there was overall improvement in anxiety and depression symptoms post-ETI, approximately 10 % of individuals experienced clinically significant worsening.