The hitherto unknown trifluoroselenoacetic acid was prepared through the reaction of trifluoroacetic acid with Woollins' reagent. The compound was fully characterized by mass spectrometry, 1H, 19F, 77Se, and 13C NMR, UV−visible, IR and Raman spectroscopy, and the boiling point at 46 °C was estimated from the vapor pressure curve. An IR matrix isolation study revealed the presence of two different syn−anti and anti−syn conformers. The IR spectra of the two stereoisomers have been assigned, aided by DFT, and ab initio calculations. The UV photolysis of Ar matrix isolated CF3C(O)SeH yielded CO, OCSe, CF3SeH, and CHF3. Apart from CF3SeH, these products were also obtained by vacuum flash-pyrolysis (310 °C) of gaseous CF3C(O)SeH. Instead of CF3SeH, CF2Se, and HF were detected among the pyrolysis products. The different decomposition pathways of CF3C(O)SeH are discussed.