The formation of synthesized Si2N2O nanowires using the process of Si nitridation depending on the addition of carbon was investigated. The diameter of the Si2N2O nanowires having a high aspect ratio of about 50–80 nm was found in the porous Si2N2O–Si3N4 substrate to which 6 wt% C was added. The synthesized Si2N2O nanowires had orthorhombic single-crystal structure covered with a thin (∼2 nm thick) amorphous layer and a large number of stacking faults along the (2 0 0) plane. The photoluminescence spectrum of Si2N2O nanowires showed a strong, stable green emission at 540 nm.