Cytochrome P450s are very versatile enzymes with great potential for biotechnological applications because of their ability to oxidize unactivated CH bonds. CYP105A1 from Streptomyces griseolus was first described as a herbicide-inducible sulfonylurea hydroxylase, but it is also able to convert other substrates such as vitamin D3. To extend the substrate pool of this interesting enzyme further, we screened a small diterpenoid compound library and were able to show the conversion of several resin acids. Binding of abietic acid, dehydroabietic acid, and isopimaric acid to the active site was assayed, and Vmax and Km values were calculated. The products were analyzed by NMR spectroscopy and identified as 15-hydroxyabietic acid, 15-hydroxydehydroabietic acid, and 15,16-epoxyisopimaric acid. As the observed products are difficult to obtain by chemical synthesis, CYP105A1 has proved to be a promising candidate for biotechnological applications that combine bioconversion and chemical synthesis to obtain functionalized resin acids.