Conductive composite foams were prepared by exposing iodine-loaded polyurethane (PU) foams to pyrrole vapor. The kinetics, equilibrium, and mechanism of the in situ polymerization of pyrrole by iodine within a PU foam was investigated. The dopant for the polypyrrole (PPy) was primarily I3−, which formed a charge-transfer complex (PPy-I2) with the amine group of the PPy. The conductivity of the composite foams increased with increasing concentration of the PPy-I2 complex and depended on the distribution of the PPy-I2 complex in the PU matrix and the concentration ratio of PPy and iodine. The chemical structure, morphology, mechanical properties, and thermal stability of the composite foams were also characterized.