Erbium doped ZrO2 nanocrystals ranging from 30 to 80 nm in size were prepared by a sol−gel process withthe presence of cationic (CTAB) and nonionic (PLURONIC P-127) surfactants, and the up-conversion emissionwas characterized. A strong green emission was produced by the transition 2H11/2 + 4S3/2 → 4I15/2 and enhanced1 order of magnitude with the presence of PLURONIC P-127 at a molar ratio Mrp = 0.0082 annealed 5 hat 1000 °C. A molar ratio of Mrc = 0.2 CTAB annealed 0 min at 1000 °C induced an increment of 300% ofthe signal emitted. In both cases the enhancement was partly attributed to the high content of monoclinicphase and crystallite size. However, the dominant parameter for the enhancement of the luminescence wasthe elimination of residual contaminants and defects produced for surface recombination.