Hydrogen peroxide (H2O2) is an important biological molecule and plays vital roles in cell growth, immune responses, and cell signaling pathways. Cellular viscosity is a significant physiological parameter and also indicates the normal or abnormal functions of cells. Moreover, both abnormal levels of H2O2 and cellular viscosity are found to be highly related to some major diseases, such as Alzheimer’s disease and cancers. Therefore, the development of effective analytical tools for simultaneously detecting H2O2 and cellular viscosity is of great significance to elucidating some critical physiological and pathological mechanisms, as well as the diagnosis of some relevant diseases. In this work, we developed a dual-responsive fluorescent probe (1) for viscosity and H2O2. Probe (1) is almost non-fluorescent due to the quenching effect arisen from the twisted intramolecular charge transfer (TICT) process within the probe. While the probe exhibited strong near-infrared fluorescence (~680 nm) in solution with high viscosities, which can be attributed the restricted TICT process. The turn-on fluorescence reached 85 folds with the solution viscosity increased from 1.996 cp to 851.8 cp. Furthermore, probe (1) also can sensitively response to H2O2 with the evolution of a new emission band at about 590 nm. H2O2 can effectively react with the phenylboronic acid moiety of probe (1) and result in the conversion of pyridinium unit to pyridine, which could attenuate the ICT (intramolecular charge transfer) and TICT effects of the probe, and thus lead to a dramatic increase in the fluorescence intensity as well as a blue-shift in absorption profile (from 540 to 460 nm) with the observed color of the solution changed from purple-red to yellow. Fluorescence measurements indicated that probe (1) is highly sensitive and selective for H2O2. The fluorescence intensity of the probe assay at 590 nm was found to vary linearly with the concentration of H2O2 in the range of 0～25 μmol·L-1, the detection limit was calculated to be 0.34 μmol·L-1 (3σ). Furthermore, cellular imaging experiment confirmed that probe (1) is highly biocompatible and cell-membrane permeable, and can be utilized for monitoring H2O2 in living cells.