The effect of annealing on the photoluminescence (PL) in GaAsSbN/GaAs quantum wells (QWs) grown by solid-source molecular-beam epitaxy has been investigated. The annealing time and temperature are 5min and 650–750°C, respectively. Low-temperature (4K) PL peaks shift to higher energies with the annealing temperatures. An As–Sb atomic interdiffusion at the heterointerface is proposed to model this effect. The compositional profile of the QW after interdiffusion is described by an error function distribution and calculated by a ten-band k∙p method. The estimated interdiffusion constants D are ∼10-17–10-16cm2/s in the above temperature range and an activation energy of 1±0.4eV is obtained.