Herein we report the synthesis of “clickable” magnetic nanoparticles (MNPs) stable in suspension in physiological media for bioorthogonal click chemistry applications. These MNPs incorporate into their coating a cyclooctynyl derivative for strain-promoted azide–alkyne (SPAAC) cycloaddition and either a polyethylene glycol or a glucose moiety to ensure MNP stability in physiological media. Their reactivity towards azide-functionalised Si surfaces was investigated, demonstrating their potential as bioorthogonal probes.