The selective hydrodefluorination of hexafluoropropene to HFO‐1234ze and HFO‐1234yf can be achieved by reaction with simple group 13 hydrides of the form EH3 ⋅ L (E=B, Al; L=SMe2, NMe3). The chemoselectivity varies depending on the nature of the group 13 element. A combination of experiments and DFT calculations show that competitive nucleophilic vinylic substitution and addition‐elimination mechanisms involving hydroborated intermediates lead to complementary selectivities.