The small leucine‐rich proteoglycan decorin can bind via its core protein to different types of collagens such as type I and type VI. To test whether decorin can act as a bridging molecule between these collagens, the binding properties of wild‐type decorin, two full‐length decorin species with single amino acid substitutions (DCN E180K, DCN E180Q), which previously showed reduced binding to collagen type I fibrils, and a truncated form of decorin (DCN Q153) to the these collagens were investigated. In a solid phase assay dissociation constants for wild‐type decorin bound to methylated, therefore monomeric, triple helical type I collagen were in the order of 10−10 m, while dissociation constants for fibrillar type I collagen were ≈ 10−9 m. The dissociation constant for type VI was ≈ 10−7 m. Using real‐time analysis for a more detailed investigation DCN E180Q and DCN E180K exhibited lower association and higher dissociation constants to type I collagen, compared to wild‐type decorin, deviating by at least one order of magnitude. In contrast, the affinities of these mutants to type VI collagen were 10 times higher than the affinity of wild‐type decorin (KD ≈ 10−8 m). Further investigations verified that complexes of type VI collagen and decorin bound type I collagen and that the affinity of collagen type VI to type I was increased by the presence of decorin. These data show that decorin not only can regulate collagen fibril formation but that it also can act as an intermediary between type I and type VI collagen and that these two types of collagen interact via different binding sites.