Study aim: The present study aimed to evaluate the effects of nano-curcumin on CF patients in order to achieve the intrinsic and extrinsic effects of curcumin on the inflammatory process in these patients. Design: This was a double-blind, randomized, placebo-controlled clinical trial. Settings and conduct: Akbar Children's Hospital in Mashhad, Iran. Participants/Inclusion and exclusion criteria: Inclusion Criteria The inclusion criteria of the study were as follows: 1) one or more typical phenotypic features of CF and a minimum of an elevated sweat chloride concentration on two/more occasions or two mutations known to cause CF on separate alleles; 2) age of 5-18 years; 3) pulmonary and gastrointestinal involvement; 4) ability to perform spirometry maneuvers and the minimum FEV1 of ≥30% compared to the same age, gender, and height in the normal population; 5) the percentage of oxygen saturation based on pulse the oximetry of ≥90% at room temperature; 6) no cardiovascular, hepatic, and renal failure; 7) absence of celiac disease and rheumatoid arthritis; 8) no acute pulmonary exacerbation requiring hospitalization within the past four weeks; 9) absence of acute respiratory tract infection; 10) informed consent for participation. Exclusion Criteria The exclusion criteria of the study were the lack of adherence to the drug regimen and presence of drug tolerance. Intervention groups: The study population consisted of the patients with known CF referring to the Cystic Fibrosis Clinic at Akbar Children's Hospital. Main outcome variables: Evaluation of inflammation at three levels: 1) systemic by assessing IL-8 as an inflammatory agent, IL-10 as an anti-inflammatory agent, and hsCRP level in the blood samples; 2) pulmonary with the neutrophil count, and bacterial/viral culture on the nasopharyngeal swab; 3) gastrointestinal with the calprotectin level in the fecal samples.