LiYF4:Tm(3+)/Yb(3+) upconverting nanoparticles (UCNPs) were functionalized with the second generation photosensitizer 5,10,15,20-tetra(m-hydroxyphenyl)chlorin (m-THPC, Temoporfin, Foscan®). m-THPC was modified using 4-(bromomethyl)benzoic acid, which induced a bathochromic shift of the m-THPC blue absorption peak. The nanoconstruct causes up to 70% cell death under 980 nm irradiation.