Comparative studies have been carried out on the cathodoluminescence (CL) and photoluminescence (PL) properties of GaN implanted with Tm and GaN co-implanted with Tm and a low concentration of Er. Room temperature CL spectra were acquired in an electron probe microanalyser to investigate the rare earth emission. The room temperature CL intensity exhibits a strong dependence on the annealing temperature of the implanted samples. The results of CL temperature dependence are reported for blue emission (∼ 477 nm) which is due to intra 4f-shell electron transitions (1G4 → 3H6) associated with Tm3+ ions. The 477 nm blue CL emission is enhanced strongly as the annealing temperature increases up to 1200°C. Blue PL emission has also been observed from the sample annealed at 1200°C. To our knowledge, this is the first observation of blue PL emission from Tm implanted GaN samples. Intra-4f transitions from the 1D2 level (∼ 465 nm emission lines) of Tm3+ ions in GaN have been observed in GaN:Tm films at temperatures between 20–200 K. We will discuss the temperature dependent Tm3+ emission in both GaN:Tm,Er and GaN:Tm samples.