In this work, we report a novel sensor for colorimetric and fluorometric HO sensing which is based on silver nanoparticles decorated and tetraphenylethene probe doped silica nanoparticles (Ag@TPE-SiO NPs). A positively charged tetraphenylethene (TPE) probe is doped into silica nanoparticles, and the nanoparticles exhibit strong fluorescence emission due to aggregation-induced emission (AIE) of the TPE probe. Ag nanoparticles (AgNPs) are prepared in situ on the surface of the silica nanoparticles. AgNPs serve as a nanoquencher which can quench the AIE emission of the TPE-SiO NPs efficiently. However, AgNPs can be oxidized to Ag by HO, which leads to fluorescence recovery and color fading of the Ag@TPE-SiO NPs. The dual-readout strategy allows sensitive analysis of HO. The detection limit of the fluorometric and colorimetric assay is 0.28 and 2.1 μM, respectively. And the nanosensor also shows good selectivity. In addition, analysis of HO in human serum and intracellular imaging of HO are both demonstrated. With the good analytical properties of merit, the proposed nanoprobe has a promising potential for HO related bioanalysis and biomedical applications.