A one-step citrate-gel combustion method was employed to process (Ba0.5Sr0.5Fe12O19)1-x/(Y3Fe5O12)x nanocomposite ferrites with different compositions (x = 0.1, 0.2, 0.3, and 0.4). The morphological, structural, thermal, and magnetic properties of the as-synthesized samples were investigated with respect to their structural, thermal, and magnetic properties using field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), thermogravimetric analysis and differential scanning calorimetry (TGA/DSC), and vibration sample magnetometer (VSM), respectively. The FESEM micrographs revealed homogeneous distribution of hard and soft magnetic phases throughout the sample. The XRD results confirmed the crystallization of both BSFO and YIG as hard and soft magnetic phases, respectively, without any other secondary phases. The TGA/DSC curve confirmed the phase formation of the nanocomposite material around 1100 °C with a total weight loss of ~ 63%. The magnetic hysteresis loops of as-synthesized ferrite nanocomposites demonstrated a single-phase behavior due to the existence of strong inter-grain exchange coupling between the hard and soft magnetic phases. The single peak in switching field distribution (SFD) curves of synthesized nanocomposite ferrite were observed for all the compositions. Maximum values of coercivity (6090 Oe), saturation magnetization (54 emu/g), and energy product (19.5 kJ/m3) were achieved for the BSFO0.9/YIG0.1 composition. The results of the present study suggest that the magnetic parameters such as those derived from the nanocomposite ferrites are superior as compared with that of those obtained for the constituent YIG and BSFO phases. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.