Transparent wood (TW) is a wood-based biomaterial with several advantages, such as high optical transmittance, low thermal conductivity, and tunable haze. TW is functionalized according to its transparency to broaden its applications in different fields. Several studies have examined wood functionalization in recent years; however, few studies have reported photochromic TW (PTW) for ultraviolet (UV) -shielding window applications. Herein, PTW was obtained by infiltrating the delignified wood template with photochromic silver bromide (AgBr) nanoparticles and a pre-polymerized methyl methacrylate (MMA) mixture solution. The obtained PTW can adjust the luminous flux on change in the color in the visible light region. The photochromic properties were examined, and the optical properties of the composites were characterized using UV-Vis spectrophotometry. Light transmittance of PTW was up to 86.5% at 800 nm before UV irradiation, and it decreased to 70.1% at 800 nm after UV irradiation, as the wood color changed from colorless to dark purple under UV irradiation. Thus, this work not only achieves high-value utilization of wood, but also produces a new material that can be used in varied fields, such as UV-shielding, energy saving, and smart building.