A series of Zn0.5Co0.25Cu0.25Ho0.037Fe1.963O4 (ZCCHF)/Graphene nanoplatelets (GNPs) nanocomposites (where GNPs = 0 wt%, 1.25 wt%, 2.5 wt%, 3.75 wt%, 5 wt%) were prepared via sol-gel auto-combustion (SGAC) method followed by bath sonication and studied their structural, morphological, optical, dielectric, and magnetic properties. The structural analysis confirmed a single-phase crystal matrix of all the as-prepared nanocomposites. The optical analysis revealed that the energy bandgap (Eg) lies within the range of 1.57 eV–1.62 eV. The dielectric analysis showed that the improvement in the dielectric constant (ε′) and reduction in dielectric tangent loss (tan δd) with increasing GNPs concentration from 0 wt% to 5 wt%. The real part of permeability (μ′) was improved and magnetic tangent loss (tan δM) was reduced with the addition of GNPs. Magnetic properties were studied at different temperatures (5 K, 300 K, and 400 K), and observed high saturation magnetization (MS), and coercivity (HC) at a low temperature (at 5 K). The low MS, and HC values were observed at high temperatures (300 K and 400 K). The combination of improved dielectric and tunable magnetic properties makes ZCCHF/GNPs nanocomposites promising candidates for applications in spintronics, high-frequency magnetic devices, and advanced electronic systems.