(Phosphine-sulfonate)Pd(Me)(DMSO) catalyzed copolymerization of ethylene and 3,3,3-trifluoropropene (TFP) allows the synthesis of linear copolymers with high fluorine contents of up to 15 wt % (8.9 mol % TFP). 13C and 19F NMR analyses of the copolymers were performed, showing that most of the incorporated TFP is located in the polymer backbone. Copolymerization of ethylene-d4 with TFP revealed that TFP is inserted into Pd-D bonds in 1,2- as well as in 2,1-mode, although 1,2-insertion is slightly preferred. Chain transfer after TFP insertion is exclusively observed following 2,1-insertion. With higher TFP incorporation, an increase in the ratio of internal to terminal double bonds was detected in the 1H NMR spectra. This indicates that, in the case of 2,1-insertion of TFP, chain walking is facilitated relative to direct chain release after β-H transfer to the palladium center.