CaTiO3:xEr(3+):yYb(3+)(x = 0.3mol%; y = 1.0, 1.5 and 2.0 mol%) was synthesized by the sol-gel process. Crystal phase purity, crystallite sizes and microstrain were evaluated as a function of rare earths concentration through XRD and SEM techniques. Upconversion (UC) spectra were recorded at 300 K under excitation at 980 nm and 1550 nm. The samples showed higher intensity of green emission assigned to the upconversion phenomena compared to the red one, when excited at 980 nm and the opposite was observed when excitation was performed at 1550 nm. The nanoparticles CaTiO3:Er3+:Yb3+ were successfully applied as animals cells cytoplasm staining luminescent probes, with low cytotoxic effect being observed. Er3+ emission at 1550 nm was also proposed for in vivo or in vivo optical imaging analysis in the so-called second window (1350-2300 nm).