A green emitting BaSiON:Eu phosphor with an appreciable intensity was synthesized using the gas-reduction–nitridation (GRN) method. SEM revealed agglomerated BaSiON:Eu particles with irregular morphologies and a primary particle size of 1–2.5 μm. The phosphor showed emission lines of Eu corresponding to the 4f5d → 4f transition under 370 nm excitation. As the GRN process was conducted to incorporate N into the lattice, both the excitation and emission intensity of BaSiON:Eu were enhanced greatly compared to BaSiO:Eu. The decay time of BaSiON:Eu showed that N entered the BaSiO:Eu lattices to replace O to form a N point defect. The electroluminescence intensity of BaSiON:Eu at 503 nm increased with increasing forward bias current. Intense green LEDs were fabricated by coating the synthesized phosphors on the cap of the near-ultraviolet InGaN LEDs (λ = 375 nm). Overall, this phosphor appears to be a promising candidate for solid-state lighting applications.