Some aspects of therapeutic action of catechins are associated with their effects on the deposition of collagen fibrils in tissues. It is assumed that this process is controlled through signaling and regulatory pathways in cells that catechins affect, however, the direct interactions of polyphenols with structural proteins cannot be excluded. The present work investigates the direct effect of (+)-catechin and epigallocatechin gallate on the formation of collagen fibrils in vitro. Turbidimetty, differential scanning calorimetry and transmission electron microscope data showed that (+)-catechin accelerates the formation of type I collagen fibrils, and the resulting fibrils have a protein-specific structure and thermal stability, while epigallocatechin gallate at a concentration of 10 μM inhibits fibrillogenesis. The results obtained expand our understanding of the potential mechanisms of therapeutic action of catechins demonstrating the possibility of a direct interaction of (+)- catechin and epigallocatechin gallate with collagen monomers and collagen fibrils and these findings may be useful in the development of new drugs containing these plant polyphenols or their synthetic analogues.