Structural changes caused by heat-treatment of newly developed electroless NiPC films were investigated. The NiPC films containing a few atom percent of carbon, which exhibit an exceptionally high resistivity (p) and an excellent temperature coefficient of resistance value were prepared by using diethylenetriamine and beta-alanine as complexing agents. The p value of this film decreased upon heat-treatment. The differential scanning calorimetry measurements showed that the NiPC films exhibit peaks which are distinct from the peaks of the conventional NiP film. The X-ray diffraction results indicated that these peaks could be associated with structural changes. In fact, observed crystallization temperatures of the NiPC films were higher than that of the NiP film. Gas components desorbed from the NiPC films during annealing were identified. It is evident that the NiPC films contain various organic elements and water. Transmission electron microscope bright-field images for the NiPC films reveal unique bean-like features. The bean-like features are retained even after crystallization and presumably affect the resistivity. The high resistivity is associated with organic elements incorporated in the film as well as the bean-like features.