Nanoparticles (NPs) enable the development of new, biologically relevant, multifunctional agents. Multifunctional NPs can mimic the invasive biological processes involved in cancer metastasis. We have demonstrated a facile and controllable method of conjugating multiple enzyme species to superparamagnetic (SPM) NPs. Horseradish peroxidase, α-glucosidase, and collagenase were conjugated to SPM NPs with a functional enzyme:NP ratio of 15:127:103:1. N-succinimidyl-S-acetylthiopropionate (SATP)-mediated addition of sulfhydryls to enzymes was achieved without significant activity loss. Conjugation of all enzymes was simultaneously accomplished using maleimide reactive groups generated from activation of amines associated with polyethylene glycol molecules on the NP surface. Cross reactivity between enzyme activity assay systems was negligible.