In this study, the adsorption characteristics together with the modified thermomechanical properties of stable BxCyNz heteronanotubes, i.e. BC2N, BC3, and NC3, in ambient conditions have been explored under the adsorption of NiTMTAA molecules (NiTMTAA/heteronanotube). Employing molecular dynamics study, it is observed that π-π stacking interaction plays a major role in the adsorption of NiTMTAA. The radius of gyration and circumferential distribution along the axis of NTs demonstrate the higher agglomeration of molecules near the wall of CNT and BC3 than that of other NTs. Moreover, it is observed that CNT and BNNT possess the highest Young’s modulus and thermal conductivity than those of heteronanotubes. According to the results, the adsorption of NiTMTAA molecules reduces thermal conductivity. Unlikely, Young’s modulus of NiTMTAA/heteronanotubes for small weight percentage of NiTMTAA molecules (<~20%) is slightly higher than pure heteronanotubes. Furthermore, it is shown that for more than 20%, the thermomechanical properties are approximately converged to the slightly lower value than that of pure heteronanotubes. Finally, it is demonstrated that the presence of both boron (B) and nitrogen (N) atoms in heteronanotubes, i.e. BC2N, results in higher thermomechanical properties than the individual presence of B and N.