With increasing focus on the structural elucidation of polymers, advanced tandem mass spectrometry techniques will play a crucial role in the characterization of these compounds. In this contribution, synthesis and analysis of methyl-initiated and xanthate-terminated poly(2-ethyl-2-oxazoline) using Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry (MS) was achieved. Electron capture dissociation (ECD) produced full end group characterization as well as backbone fragmentation including complete sequence coverage of the polymer. A method of fragment ion characterization is also presented with the use of the high-resolution-modified Kendrick mass defect plots as a means of grouping fragments from the same fragmentation pathways together. This type of data processing is applicable to all tandem mass spectrometry techniques for polymer analysis but is made more effective with high mass accuracy methods. ECD FT-ICR MS demonstrates its promising role as a structural characterization technique for polyoxazoline species.