The one-step hydrothermal reduction method was used to create platinum nanoparticle (Pt NPs)-modified molybdenum disulfide (MoS2)-silica (SiO2) nanocomposites (Pt-MoS2/SiO2) with excellent peroxidase-like activity. Results of characterization revealed the successful synthesis of Pt-MoS2/SiO2 with the diameter being about 1 μm. Steady-state kinetic experiments indicated that the catalytic behavior of Pt-MoS2/SiO2 followed the Michaelis–Menten model of enzyme kinetics and had a good affinity with the substrates. The electron spin resonance (ESR) analysis results showed that hydrogen peroxide could be decomposed into hydroxyl radicals (·OH) and superoxide radicals (·O2−) under the catalysis of Pt-MoS2/SiO2, and followed by oxidizing colorless 3,3′,5,5′-tetramethylbenzidine (TMB) into a blue oxidation product (oxTMB). However, hydroquinone (HQ) could prevent TMB from oxidizing, and the amount of fade relied on the amount of HQ. This led to the development of a quick, sensitive, and accurate colorimetric sensing device for HQ, with a linear range of 0.5–9 μM and a limit of detection (LOD) as low as 0.242 μM. Furthermore, the satisfactory sensitivity and selectivity of HQ sensing platform in tap water and river water samples endowed it as a potential candidate in real applications. Graphical Abstract: A facile and efficient sensing platform for hydroquinone was established based on the peroxidase-like activity of platinum modified core–shell molybdenum disulfide/silica nanocomposites. [Figure not available: see fulltext.].