The present work is concerned with the synthesis and studying the electrical and dielectric properties of Polyaniline (PANI)/Mn3O4/Reduced Graphene Oxide (RGO) nanocomposites using the Broadband Dielectric Spectroscopy technique. Polyaniline/Mn3O4 and polyaniline/Mn3O4/RGO nanocomposites were prepared using in-situ polymerization. To investigate the structural and morphology of the prepared samples, XRD, FTIR, HRTEM and SEM techniques were used. XRD results of pure Mn3O4 and PANI showed that PANI has crystallinity to some extent and the formation of Mn3O4 as a major phase with crystallite size ~20 nm is obtained. In case of nanocomposite samples, PANI/Mn3O4 and PANI /Mn3O4/RGO revealed a slight disappearance of the characteristic peaks of Mn3O4, which may be attributed to the covering of Mn3O4 surface by PANI. FTIR analysis of the nanocomposite samples indicated that the characteristic absorption peaks are shifted to higher wavenumbers compared with that of pure PANI confirming the interaction between PANI, graphene and Mn3O4. The morphological study of the samples revealed a porous surface of micro aggregates of Mn3O4 and PANI enveloped by RGO sheets and showed the distribution of Mn3O4 nanoparticle and PANI nanofibers on and between the thin sheets of RGO. The value of dc conductivity is rather high, and the prepared nanocomposites could be considered as synthetic metals from the conductivity point of view of such plastic electrode materials.