As part of the green transition new technologies and chemical compounds are being introduced with lower climate impact. One example is the replacement of halogenated compounds with high global warming potentials (GWPs) using compounds with low GWPs. Halogenated olefins are a family of chemicals that has been developed as alternatives to high GWP hydrofluorocarbons (HFCs). The olefinic double bond provides a reaction site for atmospheric OH radicals, lowering the atmospheric lifetime and climate impact. There is interest in the possible production of trifluoromethane (CF3H, GWP = 14,600) (IPCC, 2021) from atmospheric photolysis of CF3CHO, an oxidation product from several hydrofluoroolefins (HFOs). In addition to reaction with OH, the double bond in HFOs is reactive towards other atmospheric oxidants, including chlorine and ozone. The production of CF3H from the ozonolysis of different commercially relevant fluorinated olefins has been reported (McGillen et al., PNAS, 120, e2312714120, 2023). If CF3H is formed in the ozonolysis of HFOs, it is plausible that it would also be formed in other halogenated olefins with a CF3CH = moiety. HCFO-1233zd (CF3CH=CHCl) is a widely used hydrochlorofluoroolefin (HCFO). We report the formation of CF3H in molar yields of (6.1 ± 0.9) % and (6.4 ± 1.0) % in the ozonolysis of E- and Z-CF3CH=CHCl, respectively. This finding is discussed in the context of the contribution of halogenated olefins to the radiative forcing of climate change.