The phenomenon of optical (laser) radiation heating of nanoparticles (NP) is important for applications in laser processing of NPs (laser induced transformation in NP size, shape and structure), light-to-thermal energy conversion and nanoenergy, laser nanomedicine, thermal catalysis, and so forth. It is essential to theoretically describe the temporal and spatial–temporal behavior of the NPs and the medium temperature for the analysis of experimental results and for the theoretical prediction of the unknown dependencies and new effects. Analytical and computer descriptions of heating, melting of a single NP under the action of CW and pulsed optical (laser) radiation and NP cooling after the termination of radiation action is carried out. An analytical model developed for the description of NP heating, heat dissipation and exchange with an ambience and cooling has been examined, and its accuracy and applicability has been estimated and established.