Herein, we disclose the first utilization of mesoporous natural fiber welded (NFW) cellulose to sequester titanium dioxide nanoparticles (TiO₂NPs) from aqueous colloids, resulting in “excellent” UV-protective textiles. Because mesoporous NFW cellulose possesses a high surface area (≥200 m² g^–1) and nanometer sized pores (ca. 2–20 nm), it can be used as a scaffold for a wide variety of materials on the same scale. In this study, the mesoporous NFW cellulose encapsulates commercially available, 5 nm TiO₂NPs from colloidal suspension, promoting rapid (ca. 60 s) uptake without disruptive in situ NP formation. Furthermore, drying of the material collapses the mesopores after colloid exposure, entrapping the NPs within the mesoporous biopolymer matrix. Our methods deliver TiO₂NP at a loading of ca. 1.6 wt %, resulting in fabrics that possess ultraviolet protection factor (UPF) ratings of 200+ and are considered “Excellent” by the U.S. Food and Drug Administration (FDA). These results were compared against biopolymer controls (neat cellulose cloth and nonmesoporous NFW cellulose cloth), which possess distinctly lower UPF values of 12.1 and 41, respectively, when subjected to equivalent TiO₂NP uptake conditions (NP loadings of 6.9 and 0.8 wt %, respectively). Scanning electron microscopy (SEM) images and accompanying energy-dispersive X-ray spectroscopy (EDS) maps elucidate NP uptake within pores, showing a uniform layer of TiO₂NPs extending 3 μm into the mesoporous NFW textile surface. Ultimately, this study discloses a novel application of biopolymer engineering showing the advantage of using mesoporous NFW cellulose as a scaffold for functional biocomposites. The study not only presents a simple and scalable method to make high-performance UV-protective fabrics but also details a generalizable approach for nanomaterial entrapment using mesoporous NFW composites, so long as the size of the encapsulated material and the scaffold are complementary.