GaAso0.949N0.051/GaAs multiple quantum wells (MQWs) were grown on GaAs (001) substrates by metalorganic vapor phase epitaxy (MOVPE). Strong photoluminescence (PL) emission around the 1.3-μm-wavelength region was observed without post-growth thermal annealing, which suggests an efficient electron confinement in the GaAso0.949N0.051/GaAs MQWs. After post-growth thermal annealing, blue-shift of PL peak energy was clearly observed. This PL blue-shift, induced by thermal annealing, can be described by diffusion of N out of the quantum well and homogenization of the N concentration fluctuation. Furthermore, a reduction of PL full width at half maximum (FWHM) suggests the more homogeneous N distribution. In addition, both the as-grown and annealed GaAso0.949N0.051/GaAs MQWs exhibit fairly flat and abrupt GaAsN/GaAs interfaces, which were confirmed by high resolution x-ray diffraction (HRXRD) and transmission electron microscopy (TEM) measurements. Based on PL results, it is evident that the band alignment of GaAsN/GaAs hetero-structure is a type-I band lineup. Adding N to GaAs mainly affects the conduction band (CB) states leading to a large conduction band offset (△Ec ∼ 550 meV). Our results show the potential for the fabrication of 1.3 μm GaAsN QW lasers on GaAs substrates.