Room-temperature active catalysts are very important to combat against ubiquitous indoor HCHO pollution. Here, tungsten doped MnO₂ (W-MnO₂) was first synthesized and investigated for HCHO decomposition at ambient temperature. With addition of WCl₆ as precursor into the mixture of permanganate and manganese chloride, tungsten-doped δ-MnO₂ with weak crystallinity and large specific surface area (>230 m²/g) was synthesized. Substitution of W⁶⁺ for Mn in MnO₆ groups reduced the chemical valence of Mn and made adsorbed surface oxygen species more active. As a result, the W-MnO₂ catalyst with the nominal W/Mn ratio achieved efficient and stable activity for real-level indoor HCHO (0.3 mg/m³) under the GHSV as high as 600 L/g_cat·h, the removal efficiency reaching 90% at 30 °C and 60% at 5 °C, respectively.