In this report, the influence of thermal annealing of thin P3HT films and P3HT:C-60 composites were studied regarding their morphology and structural properties. Atomic force microscope measurements on P3HT films and P3HT:C-60 composite disclose some variation in morphology during annealing due to the crystallization of C-60. The as-prepared P3HT:C-60 films have a higher surface roughness and larger cluster size compared to the as-prepared P3HT films. The thermal annealing effects on the optical microscopy indicate that the polymer shows improved capability to self-organize. Their structural properties were studied by X-ray diffraction analysis. It was found that the crystallinity of the investigated films is drastically increased upon annealing and a decrease in the grain sizes is observed.