Stable and easily-handled synthetic materials mimicking natural enzymes activity would find important biotechnological applications. This article describes the synthesis and characterization of magnetic molecularly imprinted catalytic polymers that exhibit peroxidase-like activity towards 5-hydroxyindole-3-acetic acid (5-HIAA) oxidation. This multifunctional material is obtained from highly crystalline magnetite nuclei coated with a silica layer to protect the iron nucleus from oxidation and to provide anchoring for hydroxyl surface groups. After acrylic functionalization via sal gel process, a molecularly imprinted polymer with hemin as catalytic center and 5-HIAA as template has been successfully attached to the structure. The resulting hybrid composite is magnetically separable and possesses excellent catalytic ability for the selective oxidation of the indoleamine metabolite tumor marker, showing Michaelis Menten kinetics with this molecule but not towards other structural analogs. Therefore, it can be considered an artificial peroxidase enzyme. (C) 2014 Elsevier Ltd. All rights reserved.