The increased demand for the discovery of new conducting materials encourages the researchers for the development of advanced electronic technologies. In the present study, nanocomposites of poly (anthranilic acid- co-indole)/(PANA- C o-PIN) and magnetite nanoparticles (Fe3O4) were prepared via a one-step polymerization method and evaluated by various analytical techniques. The Fourier transform infrared spectroscopy (FT-IR) spectra proved the presence of Fe3O4 nanofillers in the copolymer at 507 cm−1. Optical characterization (UV-Vis) shows a clear blueshift indicating strong interactions between Fe3O4 and PANA- C o-PIN. The X-Ray diffraction (XRD) patterns revealed an increase in crystallinity due to the well dispersed nanoparticles. FESEM images evidenced the morphological changes caused by the uniform dispersion of nanoparticles in the copolymer matrix. The nano-dispersion of magnetite nanoparticles in the copolymer was confirmed by High-resolution transmission electron microscopy analysis. Magnetic properties of nanocomposites obtained from a vibrating sample magnetometer (VSM) showed an increase in the saturation of magnetism with the addition of nanoparticles and the composite exhibited superparamagnetic behaviour. The thermal stability and glass transition temperature of the nanocomposites were greatly enhanced with the addition of nanoparticles and were determined with the help of Thermogravimetric Analysis (TGA) and Differential scanning calorimetry (DSC) respectively. Filler-dependent electrical properties showed a linearly increased DC conductivity with the addition of nanoparticles. The impedance analysis showed that the AC conductivity and dielectric properties of the nanocomposites were higher than the copolymer and the maximum electrical properties were observed for 15 wt.% of composites. The ammonia gas sensing performance of copolymer composite indicates the easy access of gas molecules to the sensor surface through the metal oxide nanoparticles. The synthesized copolymer nanocomposites showed high sensitivity and fast response to ammonia gas. The prepared composite with good thermal properties, dielectric constant, ammonia gas sensing and magnetoelectric properties is a promising candidate for use in nanoelectronics devices.