The reaction rate kinetics of the thin film solid-state reaction between 120 nm of Pd and 100 or 300 nm of a-Si:H(18 at%) to form Pd2Si were studied in situ using x-ray diffraction and four-point probe resistivity measurements during isothermal annealing. These two techniques yielded activation energies and prefactors of Ea = 1.36±0.11 eV with k0 = 4.29 cm2/sec for the x-ray diffraction experiments; and Ea = 0.97±0.22 eV with k0 = 3.42×10-4 cm2/sec for the resistivity measurements. The activation energy and prefactor obtained from the c-Si substrate of the resistivity measurements yielded Ea = 1.41±0.31 eV and k0 = 10.6 cm2/sec. Comparisons showed that the silicide formed from the a-Si:H reacted approximately 1.4 times faster than the silicide formed from the c-Si in the same sample, but three times faster than silicide formed on pure c-Si(111). The crystalline texture and grain size of the metal and silicide films were examined.