Overall thermal rate coefficients for the CH2CO + O (3P) ⟶ CH2 + CO2 reaction were estimated by combining the canonical variational theory with multidimensional small-curvature tunneling corrections (CVT/SCT) and multifaceted variable-reaction-coordinate transition state theory (VRC-TST) results. The energies, equilibrium geometries, and harmonic vibrational frequencies were calculated at M06-2X/aug-cc-pVTZ level of theory. Our thermal rate constants show excellent agreement with experimental data confirming the CH2 + CO2 as the most favorable channel. Fitted total thermal rate coefficients into a modified Arrhenius equation shows a temperature-dependent activation energy. Display omitted •Thermal rate constants for CH2CO + O (3P) reaction.•Energetic, structural and spectroscopy parameters at M06-2X/aug-cc-pVTZ.•The products CH2 and CO2 are most favorable.•Activation energy is temperature-dependent.