An atomistic model for the effect of carbon (C) doping on the structural reorganization of boron suboxide (B6O) was developed from first principles density functional theory. The results indicate that it is energetically preferable for a single C atom to substitute into an oxygen (O) site rather than a B site. The lattice parameters and cell volume increase to relieve the residual stress created by the C substitution. Interstitial substitutions are not favorable for single atom substitutions. However, when 2 C atoms replace 2 neighboring O atoms within the B6O unit cell, it becomes energetically favorable to dope an interstitial O, B, or C atom along the C-C chain. If the interstitial dopant is either B or C, a local boron carbide (B4C)-like structure with either a C-B-C or C-C-C chain is created within the B6O unit cell, which could serve as an intermediate phase in the transformation of B6O into B4C. By promoting the formation of a local B4C-like structure, it may be possible to improve the mechanical stability and elastic properties of B6O.