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Dielectric barrier discharge ionization (DBDI) for mass spectrometry (MS) is still limited in terms of the upper mass range, the polarity of compounds that can be readily ionized, and thus the sensitivity. In this study, we studied the influence of several parameters, including the geometry and nature of the electrode and dielectric materials, on the performance of a DBDI source. We found that the electrode material had almost no impact on the ionization capability of DBDI. With increasing dielectric constant ϵ of the dielectric material, an improved performance could be achieved in terms of the mass range of ionizable molecules, which was found to be solely dependent on the choice of dielectric material. Increasing the voltage had little effect on expanding the mass range but instead produced more fragment ions. We were also able to ionize more polar compounds: the detection of nonapeptide-1 and the tryptic fragments of human serum albumin (HSA) became possible using DBDI-MS with a high-ε dielectric. The Table of Contents graphic depicts that with an increasing permittivity dielectric improved performance can be achieved in terms of the mass range of ionizable molecules.