Temperature dependent luminescence, lifetimes and magnetic circularly polarised luminescence (MCPL) are reported between 1.7 and 80 K and in magnetic fields of 0-5 T for [Ir(ptz)3]. Data analysis reveals the temperature and field dependent behaviour is due to the sublevel structure of the emitting state. We have determined energy separations of ΔEII,I = 10 cm-1 and ΔEIII,I = 45 cm-1 between three triplet sublevels, with intrinsic luminescence lifetimes of τI = 160 μs, τII = 10 μs and τIII = 800 ns. We compare these with values for the green emitter, [Ir(ppy)3] and discuss implications for the excited state geometries.