Coordination complexes of collagen with copper (II) sulfate were synthesized at different ratios of the starting materials. For the synthesis, a collagen solution was used, isolated from the skin of cattle, and then freed from electrolytes by dialysis. With an increase in the salt content, the yield of the reaction product increases. The composition and structure of the complex were determined by FT-IR spectroscopy, SEM, X-ray phase analysis, and differential scanning calorimetry. The complex is formed due to the coordination interaction of with the nitrogen and oxygen atom of collagen and water. An inadequate change in the composition of the complexes with a change in the initial ratio of the components was found. With an excess of collagen, some of it does not bind into a complex and precipitates. With an excess of salt, almost all of the collagen is bound into a complex and a rhombic single crystal is formed. The composition of the complex changes not due to a change in the coordination number , but due to an increase in the amount of these ions. An X-ray phase analysis of the starting materials and complexes has been carried out. The correspondence of the parameters of the crystal structure in the X-ray spectra of the complexes was found for a wide ratio of the starting materials. The synthesized complexes have been successfully used for dyeing textile materials.