Cystic fibrosis (CF), an autosomal recessive genetic disease, is recognized as one of the most prevalent diseases in Caucasian populations. Epidemiological data show that the incidence of CF varies between countries and ethnic groups in the same region. CF occurs due to pathogenic variants in the gene encoding cystic fibrosis transmembrane conductance regulator (CFTR), located on chromosome 7q31.2. To date, more than 2,000 variants have been registered in the CFTR database. The study of these variants leads to the diagnosis and the possibility of a specific treatment for each patient through precision medicine. In this study, complete screening of CFTR was performed through next-generation sequencing (NGS) to gain insight into the variants circulating in the population of Rio de Janeiro and to provide patient access to treatment through genotype-specific therapies. Samples from 93 patients with an inconclusive molecular diagnosis were subjected to full-length screening of CFTR using an Illumina NGS HiSeq platform. Among these patients, 46 had two pathogenic variants, whereas 12 had only one CFTR variant. Twenty-four variants were not part of our routine screening. Of these 24 variants, V938Gfs∗37 had not been described in the CF databases previously. This research achieved a molecular diagnosis of the patients with CF and identification of possible molecular candidates for genotype-specific treatments.