In this article we demonstrate that hybrid nanogels can be prepared by encapsulation of reactive nanoparticles (NPs) directly during nanogel synthesis. Nanogels investigated in present study consist of poly(N-vinylcaprolactam-co-(2-acetoacetoxyethyl) methacrylate) copolymer. The modification of the LaF3:Eu nanoparticle surface with reactive double bonds allows effective incorporation of the NPs into the nanogel structure. This approach ensures effective encapsulation of varying amounts of NPs into the nanogel interior with a loading efficiency close to 95%. The NPs are covalently bound to the nanogel core, and no NP leakage occurs. Reactive NPs act as multifunctional cross-linking agents and increase the cross-linking degree of the nanogels. We demonstrate the possibility of the incorporation of LaF3 nanoparticles doped with different ions (Eu, Tb, Pr, Gd) or nanoparticle mixtures into nanogels. These nanogels exhibit temperature-sensitive properties and superior colloidal stability in water and other aqueous media.