Bioorthogonal chemistries have provided tremendous insight into biomolecule structure and function. However, many popular bioorthogonal transformations are incompatible with one another, limiting their utility for studies of multiple biomolecules in tandem. We identified two reactions that can be used concurrently to tag biomolecules in complex environments: the inverse-electron-demand Diels-Alder reaction of tetrazines with 1,3-disubstituted cyclopropenes, and the 1,3-dipolar cycloaddition of nitrile imines with 3,3-disubstituted cyclopropenes. Remarkably, the cy-clopropenes used in these transformations differ by the placement of a single methyl group. Such orthogonal-ly reactive scaffolds will bolster efforts to monitor multi-component processes in cells and organisms.