The Ce3+- and Sm3+-co-doped NaBa4(BO3)(3) phosphors were synthesized by a traditional high-temperature solid-state reaction method. The morphology of NaBa4(BO3)(3) phosphors was characterized by scanning electron microscope. The crystal structures of Ce3+- and/or Sm3+-doped NaBa4(BO3)(3) phosphors were studied by X-ray powder diffraction. The results suggested that Ce3+ occupied the two Ba sites, while Sm3+ might enter into the interstices of NaBa4(BO3)(3) crystal. The four emission lines of Ce3+ situating at two Ba2+ sites can be well distinguished by Gaussian fitting. The emission lines from Sm3+ in NaBa4(BO3)(3) were significantly enhanced by 25-fold when co-doped with 1 mol% Ce3+ ions. New Sm3+ emission center characterized by the intensified excitation band at around 472 nm was produced as a result of Ce3+ co-doping, which significantly extended the excitation wavelength region for matching both the near-ultraviolet and blue-light-emitting diodes.