We report thein vitrocharacterization andin vivoevaluation of a novel89Zr-labeled radioimmunoconjugate synthesized using a site-selective bioconjugation strategy based on the oxidation of tyrosinase residues exposed by the deglycosylation of the IgG and the subsequent strain-promoted oxidation-controlled 1,2-quinone cycloaddition between these amino acids andtrans-cyclooctene-bearing cargoes. More specifically, we site-selectively modified a variant of the A33 antigen-targeting antibody huA33 with the chelator desferrioxamine (DFO), thereby producing an immunoconjugate (DFO-SPOCQhuA33) with equivalent antigen binding affinity to its parent immunoglobulin but attenuated affinity for the FcγRI receptor. This construct was subsequently radiolabeled with [89Zr]Zr4+to create a radioimmunoconjugate — [89Zr]Zr-DFO-SPOCQhuA33 — in high yield and specific activity that exhibited excellentin vivobehavior in two murine models of human colorectal carcinoma.