A simple, one‐pot procedure is reported for the selective defluoroalkylation of trifluoromethyl alkene derivatives with aldehydes and ketones. The reaction sequence allows construction of a new C−C bond in a highly selective manner from a single sp3 C−F bond of a CF3 group in the presence of sp2 C−F bonds. The scope incorporates industrially relevant fluorocarbons including HFO‐1234yf and HFO‐1234ze. No catalyst, additives or transition metals are required, rather the methodology relies on a recently developed boron reagent. Remarkably, the boron site of this reagent plays a dual role in the reaction sequence, being nucleophilic at boron in the C−F cleavage step (SN2’) but electrophilic at boron en route to the carbon–carbon bond‐forming step (SE2’). The duplicitous behaviour is underpinned by a hydrogen atom migration from boron to the carbon atom of a carbene ligand.