1,1,1,2-Tetrafluoroethane dimer was investigated by pulsed jet Fourier transform microwave spectroscopy. One conformer, stabilized through a network of four C-H center dot center dot center dot F-C interactions, was observed, although several almost isoenergetic configurations were suggested by ab initio calculations. The measurements, extended to four C-13 species in natural abundance, allowed determination of the carbon skeleton structures and evaluation of the weak hydrogen bond parameters. Information on the dissociation energy is also provided.