Systematic investigation on the π-bond strengths of fluorinated ethylenes has been carried out. Computed barriers for thermal CC bond rotation of fluoroethylenes are in good agreement with existing experimental data. The π-bond strengths obtained using Benson’s procedure show the same trends as the computed CC bond rotational barriers. Stabilization of ethylene and the singlet biradical rotational transition state due to fluorine substitution are analyzed. Qualitative explanation of the change in the π-bond strength in a series of fluorinated ethylenes is provided.