In this study, a new fluorescent probe (LR1) for lysosomal HOCl was developed by integrating a morpholine moiety, a lysosome-targeting group, into the rhodamine framework. LR1 exhibited remarkable fluorescence intensity enhancement at 582 nm upon HOCl titration with a low detection limit (2.6 nM), which indicated that the probe may be capable of monitoring HOCl fluctuations at trace levels. Moreover, the probe was applied in cellular fluorescence imaging, and the results demonstrated that it could sense endogenous HOCl with low cytotoxicity in RAW264.7 cells. In addition, LR1 was found to be capable of monitoring HOCl changes in lysosomes owing to the introduction of morpholine, which served as a lysosome-targeting group. We expect that the probe has great potential as a practical molecular tool for exploring HOCl-related biology in lysosomes.