The reduction of nitroarenes is usually catalyzed by heterogeneous catalysts. In this work, highly stable aqueous dispersions of monodisperse Pt, Pd, and Au nanoparticles stabilized by thermosensitive polymer, poly(N-isopropylacrylamide) (PNIPAM), are conveniently synthesized with the average sizes of 2.3, 3.1, and 2.3 nm, respectively. The modulation of the hydrophilic-hydrophobic nano-environments of the catalysts can be selectively provided by utilizing the temperature-responsive characteristics of PNIPAM. They are effective and thermosensitive pseudohomogeneous catalysts for nitroarenes reduction. The decreasing trend of catalytic activity is as follows: PNIPAM-Au > PNIPAM-Pd > PNIPAM-Pt. The catalytic reduction of nitrobenzene (NB), 4-nitrophenol (4-NP), and o-nitroaniline (o-NA) follow the pseudo-first-order kinetics, and the catalytic rates can be tuned by utilizing their temperature-responsive behavior. PNIPAM-Au nanocatalysts exhibit high turnover frequencies (TOF) up to 84, 12.9, and 40 min−1 for catalytic reduction of NB, 4-NP, and o-NA at 20 °C, respectively, which are one of the highest values ever reported.