Objective To investigate the relationship between calcidiol (25(OH)D3) concentrations and iron parameters in patients with chronic kidney disease. Methods This is a cross-sectional, descriptive, and quantitative study. The sample consisted of 86 adult patients of both sexes undergoing dialysis. 25(OH)D3 concentrations were determined by chemiluminescence; food consumption was assessed using 24-hour recalls, and the serum levels of hemoglobin, iron, ferritin, and transferrin saturation were assessed. Data analysis was performed using the program Stata, with a significance level of p<0.05. Results The results pointed to 25(OH)D3 concentrations compatible with sufficiency, iron levels consistent with normality, and ferritin and transferrin saturation above the reference values. The consumption of carbohydrates and lipids was higher in females. There was no relationship between the adequacy of 25(OH)D3 and the presence of anemia and iron parameters. Conclusion Considering that the mean serum levels of iron and 25(OH)D3 were adequate, it is suggested that resistance to erythropoietin and the inflammatory process may have contributed to the percentage of anemic individuals found in the study.