NaYF4:Yb3+, Er3+/ZnO composite nanofibers have been prepared using the electrospinning method. A phase transfer process from cc to 13 of NaYF4 occurred after calcination treatment, which provided a simple and effective way to enhance the upconversion luminescence of the nanosized NaYF4:Yb3+, Er3+. The up-conversion emission intensity of the NaYF4:Yb3+, Er3+/ZnO composite nanofibers increased with an increase in the sintering temperature. The fluorescence intensity ratio (FIR) technique, based on the green up-conversion emissions of the NaYF4:Yb3+, Er3+/ZnO composite nanofibers, has been studied as a function of temperature. In the temperature range of 300-650 K, the maximum sensitivity and temperature resolution is approximately 0.0049 K-1 and 0.3 K, respectively, which indicates that NaYF4:Yb3+, Er3+/ZnO is a promising material for applications in optical temperature sensing. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.