The ability to chemoselectively modify either the peptide backbone or specific side chains is critical to advance the fields of bioconjugation and peptide pharmaceuticals. Transition-metal catalysis has been widely used in peptide and protein derivatization but mostly under homogeneous conditions. Herein, we present a first-in-class heterogeneous catalytic approach for the site-selective functionalization of histidine-containing peptides with aryl and alkenyl moieties bearing fluorescent and affinity tags, lipids, and conjugation handles. This heterogeneous derivatization strategy employs a copper(II) hexacyanometallate to catalyze the Chan-Lam reaction with boronic acids at either the backbone or the histidine imidazole, thus providing novel results that differ from those previously reported for the homogeneous Cu(OAc)