Ba0.5Sr0.5Fe12O19/Y3Fe5O12 (BSFO/YIG) nanocomposite ferrite with hard (BSFO) and soft (YIG) magnetic phases, were prepared by the two-step co-precipitation method. The soft magnetic phase was introduced in different weight ratios (x= 0.0, 0.1, 0.2, 0.3, 0.4 and 1) in the (1-x)Ba0.5Sr0.5Fe12O19/(x)Y3Fe5O12 nanocomposite ferrites. The structural, morphological and magnetic properties of nanocomposite ferrites were analyzed by x-ray diffraction (XRD), high-resolution transmission electron microscope (HR-TEM) and room temperature vibrational sample magnetometer (VSM). The presence of the hard and soft phase have been confirmed without any secondary phase from the XRD analysis, indicating the formation of nanocomposite ferrite. The crystallite size is found to be in the range of 45-55 nm calculated by Scherrer's formula. The HR-TEM revealed hexagonal platelets of BSFO with YIG particles with an average particle size of 90 nm formed at the surface of the (0.9)BSFO/(0.1)YIG nanocomposite. The room temperature magnetic properties of the nanocomposite, such as saturation magnetization (Ms), squareness ratio (Mr/Ms), coercivity (Hc) and nucleation field (Hn) were evaluated by employing VSM. The magnetic measurements have displayed an enhancement in coercivity and magnetization for (0.9)BSFO/(0.1)YIG. Compared with pure BSFO, the optimized (0.9)BSFO/(0.1)YIG nanocomposite showed 57% enhancement in energy product (BH)max, indicating that the nanocomposite possessed excellent exchange coupling. To investigate the exchange coupling between the hard and soft magnetic phases, dM/dH values were plotted using the demagnetization curves which indicated the effective exchange coupling effect between the hard and soft phases. © 2020 IOP Publishing Ltd.