Copper (Cu) is required for all basic biochemical and physiological processes. The aim of this study was to evaluate the effects of different sources of dietary Cu on the histomorphometry of liver and jejunal epithelium in adult rats. Male 12-week-old rats were used in a 12-week experiment. The control diet provided the required Cu level from sulfate, and other two diets were supplemented with Cu as a glycine complex at 75% and 100% of daily requirement. Basal hematological and plasma biochemical analyses were also performed. There was no effect of Cu supplementation on the liver weight and the plasma and liver Cu concentration. Histomorphometric analysis of liver tissue showed an increase in the collagen amount and intracellular space in the group supplemented with Cu amino acid. Cu given in the organic form at 100% of daily requirement decreased the muscular and submucosa layer and the crypt depth. In turn, organic copper given at 75% of daily requirement did not influence the intestinal morphology. Dietary Cu given to adult rats as copper sulfate or a glycine complex meeting 100% of the daily requirement appears to be less harmful with regard to intestinal epithelium than when given as a glycine complex at 100% of daily requirement.