The dielectric properties of single crystal and polycrystalline SrTiO3 (ST) were investigated from 295 to 4 K. Relative permittivity (εr) and loss tangent (tan(δ)) were measured systematically as a function of direct current (DC) voltage (0 V/cm to 800 V/cm), frequency (100 Hz to 1 MHz), and temperature (295 K to 4 K) for type (100) single crystal SrTiO3 (SC-ST) and for polycrystalline SrTiO3 (PC-ST). Calculated equivalent series resistance (ESR) data are also reported. Overall, the permittivity of ST showed a dependence on temperature, DC voltage, and frequency. Dependences on voltage and frequency were only observed at temperatures below about 40 K. Curie–Weiss temperature (Tcw) was found to be independent of measurement frequency and applied DC field for SC-ST and PC-ST. Two frequency-dependent ESR peaks were observed for the SC-ST. There were five such peaks for PC-ST including the same two peaks displayed by SC-ST. All loss peaks were found to follow an Arrhenius type behavior. While certain peaks might be related to structural phase transitions, the additional peaks observed for PC-ST were attributed to the presence of grain boundaries, domains, residual porosity, impurities, or their combined effects. The results provide a good prediction of the dielectric performance of SrTiO3 based capacitors towards optimizing the design of circuits used for cryogenic electronic applications.