We report herein a caged luciferin probe Cy-Hy as a sequentially activated probe to selectively and sensitively sense L-Cys and H₂O₂. The probe displayed fluorescence and bioluminescence responses toward the two analytes. Utilizing the present probe, cellular excess L-Cys-induced H₂O₂ up-regulation was observed for the first time in living MDA-MB-231 cells.