An ab initio computational study of the properties of a hydrogen-bonded complex formed between the helium-containing compound HHeF and CO was undertaken at the MP2/6-311++G(2d,2p), MP2/6-311++G(2df,2pd) and MP4(SDQ)/6-311++G(2d,2p) levels of theory. The complex CO⋯HHeF was found to be stable with a zero-point vibrational energy corrected binding energy of 5.8 kJ mol−1 (MP2) with respect to the monomer subunits. However, the other possible isomer OC⋯HHeF was optimised to a structure with two imaginary frequencies. The CO⋯HHeF complex has a large vibrational harmonic blue shift of the He–H stretch, accompanied by shortening of the He–H bond. The blue shift is explained by primarily considering the effect of the electrostatic interaction between the monomers and the electron density transfer from CO to HHeF.