We developed novel fluorogenic probes for no-wash live-cell imaging of proteins fused to PYP-tag, which is a small protein tag recently reported by our group. Through the design of a new PYP-tag ligand, specific intracellular protein labeling with rapid kinetics and fluorogenic response was accomplished. The probes crossed the cell membrane, and cytosolic and nuclear localizations of PYP-tagged proteins without cell washing were visualized within a 6-min reaction time. The fluorogenic response was due to the environmental effect of fluorophore upon binding to PYP-tag. Furthermore, the PYP-tag-based method was applied to the imaging of methyl-CpG-binding domain localization. This rapid protein-labeling system combined with the small protein tag and designed fluorogenic probes offers a powerful method to study the localization, movement, and function of cellular proteins.