We report a plug-and-play strategy for the preparation of functionally enhanced antibodies with a defined average degree of conjugation (DoC). The first stage (plug) allows the controllable and efficient installation of azide groups on lysine residues of a native antibody using 4-azidobenzoyl fluoride. The second step (play) allows for versatile antibody functionalization with a single payload or combination of payloads, such as a toxin, a fluorophore, or an oligonucleotide, via copper-free strain-promoted azide-alkyne cycloaddition (SPAAC). It is notable that in comparison to a classical N-hydroxysuccinimide ester (NHS) strategy, benzoyl fluorides show faster and more efficient acylation of lysine residues in a PBS buffer. This translates into better control of the DoC and enables the efficient and fast functionalization of delicate biomolecules at low temperature.