La2O2CN2:Er3+and La2O2CN2:Er3+/Yb3+ upconversion (UC) luminescence nanofibers were successfully fabricated via cyanamidation of the respective relevant La2O3:Er3+ and La2O3:Er3+/Yb3+ nanofibers which were obtained by calcining the electrospun composite nanofibers. The morphologies, structures, and properties of the nanofibers are investigated. The mean diameters of La2O2CN2:Er3+ and La2O2CN2:Er3+/Yb3+ nanofibers are 179.46 ± 12.58 nm and 198.85 ± 17.07 nm, respectively. It is found that intense green and weak red emissions around 524, 542, and 658 nm corresponding to the 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4Il5/2 energy levels transitions of Er3+ ions are observed for La2O2CN2:Er3+ and La2O2CN2:Er3+/Yb3+ nanofibers under the excitation of a 980‐nm diode laser. Moreover, the emitting colors of La2O2CN2:Er3+ and La2O2CN2:Er3+/Yb3+ nanofibers are all located in the green region. The upconversion luminescent mechanism and formation mechanism of the nanofibers are also proposed.