Near-infrared (NIR) photoinduced chemical processes are highly attractive for specific applications owing to the deep penetration of NIR into the nontransparent materials including biological and synthetic materials. Robust NIR photo-induced atom transfer radical polymerization (photoATRP) was achieved using upconversion nanoparticles (UCNPs) as an internal light converter to turn a 980 nm NIR light to the wavelength of UV/vislight. This NIR photoATRP was capable of polymerizing both hydrophobic and hydrophilic monomers at a low loading of ppm concentrations of the CuBr2/tris(2-pyridylmethyl)amine catalyst under the irradiation of a 980 nm NIR light (4 W/cm(2)) and UCNPs with reusable performance, providing well-defined polymers with predetermined molecular weight, low dispersity, and excellent chain-end fidelity. The switching of light "on/off" showed an excellent temporal control of the polymerization. The NIR photoATRP exhibited excellent penetrations through several visible light-proof barriers using NIR light, and it may provide future directions of photopolymerization in nontransparent systems, especially biological systems containing photosensitive moieties.