IntroductionProper transfer of patients from pediatric to adult chest clinic has critical importance. In this study, we aimed to evaluate the follow‐up data of the patients in the first 12 months after transfer.MethodsCystic fibrosis (CF) patients previously transferred to adult chest clinics were included. Demographic and clinical data were retrospectively reviewed. The baseline visit was defined as the first visit at the adult center. One‐year follow‐up data were compared with the baseline data.ResultsA total of 118 patients were included in the study (men/women: 70/48). The mean ages at the time of transfer and inclusion in the study inclusion were 26.5 (23–29) and 27.6 ( ± 6.4) years, respectively. There was a significant reduction in FEV1 (%) and FEV1/FVC ratio between baseline and 1‐year follow‐up visits (p < 0.001, p < 0.001, respectively). Compared to the year before the transfer, total number of exacerbations (p = 0.001), outpatient clinic visits (p < 0.001), total antibiotic days (p < 0.001), and intravenous antibiotic days (p = 0.001) significantly increased.ConclusionsThe findings of this study show that the pulmonary functions of CF patients decline and clinical conditions deteriorated after the transfer to the adult clinic. Simple transfer, rather than transition, may be one of the reasons for adverse outcomes in this patient population.