Polarization switching dynamics in polydomain epitaxial barium titanate (BaTi O3) thin films were investigated over the temperature range of 293-363 K. To determine domain dynamics, the transient response of the linear electro-optic effect was measured as a function of bias field under pulsed excitation and temperature. Upon removal of the bias pulse, domain backswitching is observed, which is described by the Kohlrausch-Williams-Watts (KWW) extended exponential function in time. From the KWW kinetic parameter 〈τ〉 and its temperature and field dependences, the activation field and nucleation energy for polarization reversal are determined. The measured thermal energy barrier for nucleation is in the range of 0.1 eV-0.3 eV and decreases with the electric field. These values are in good agreement with those recently obtained in molecular dynamics simulation studies of domain nucleation and growth in BaTi O3. © 2009 American Institute of Physics.