Abstract Yttrium titanate (YTO) thin films doped with rare earth elements have been deposited using the aerosol–gel process. The up-conversion emission (UPE) of films doped with erbium and/or thulium has been studied with respect to the film crystallization degree and rare earth concentration. The effects of ytterbium codoping have been considered as well. Mechanisms that control UPE of YTO films are discussed with respect to the experimental conditions. It is shown that films, which selectively emit in the blue ( 1G 4→ 3H 6 transition of thulium ions), green ( 2H 11/2→ 4I 15/2 and 4S 3/2→ 4I 15/2 transitions of erbium ions), or red ( 4F 9/2→ 4I 15/2 transition of erbium ions), can readily be achieved.