Given the association between chronic sodium losses and growth parameters and establishment of normal weight gain and linear growth in patients with cystic fibrosis (CF), in this study, we aimed to evaluate the sodium status in Iranian CF patients and its association with their growth parameters.In this prospective cross-sectional study, 44 children with CF were included. Serum and urinary sodium and creatinine levels were measured in patients, and the fractional excretion of sodium was calculated. The patients categorized in groups with FENa 1.5%. Growth parameters were compared in the group, and its association with FENa level was evaluated.In this study, 44 (27 boys and 17 girls) children with CF were included. Mean age of the studied population was 55.63 (33.2) months. In the studied patients with CF, 90.9% had a z score of -2_+2 (normal range) for BMI, 72.7% for weight, and 70% for height. From children with CF, 18 (40.9%) had FENa less than 0.5, 17 (38.6%) had FENA between 0.5-1.5, and 9 had FENa >1.5. From studied patients with CF, 16 (88.9%) had normal serum Na levels, but the FENa was ≤0.5. Based on the Spearman correlation test, there was not any significant correlation between FENa classification and the Z score of weight (P=0.92), height (P=0.83), and BMI (P=0.99).Our findings indicated that most patients with a low level of FENa had normal serum sodium levels. We did not find a significant association between FENa and growth parameters. The association had a trend to be significant for BMI. It is suggested that it may be due to appropriate follow-up of the studied population. However, it is recommended to plan more studies by including healthy subjects to obtain results that are more accurate.