Films of polyaniline (PANI) and polyaniline–CNTs composites have been synthesized by solution casting technique. Fourier transform infrared spectroscopic studies of PANI and PANI–CNTs composite films indicated the presence of interaction between CNTs and molecular chains of PANI. Dielectric properties of PANI and composite films have been investigated in the frequency range of 8.0–12.0 GHz. The real part of permittivity ( ε′) and loss factor (tan δ) were found to be higher in PANI–CNTs composite films as compared to the PANI film. The increasing behavior of ε′ and tan δ has been attributed to the interaction present between CNTs and PANI molecular chains and increase of conductivity of PANI films after incorporation of CNTs.