Ferrite–polymer composites, which merge the magnetic properties of ferrites with the flexibility of polymers, present a remarkable combination of strength and versatility, unlocking opportunities for innovative applications. In this study, NiGd_0.1Fe_1.9O₄ spinel ferrite nanoparticles were synthesized by adopting a hydrothermal method. Synthesized nanoparticles were then incorporated into a nylon 11 matrix to form a NiGd_0.1Fe_1.9O₄/Nylon composite using the tape casting method. The addition of spinel ferrite nanofillers enabled precise tuning of the electromagnetic shielding properties of the composites. Transmission electron microscopy (TEM) shows the polyhedral crystal structure of the synthesized nanoparticles with an average particle size of 20 nm. BET analysis shows mesoporous nanoparticles with a specific surface area of 40.701 m²/g. X-ray diffraction (XRD) with Rietveld refinement confirmed the formation of single crystal phases, which corresponds to the Fd3m space group with a lattice constant of 8.3614 Å. The FTIR spectrum with an absorption band of around 400–600 cm^-1 revealed the vibration of positive ions at tetrahedral and octahedral sites, characteristic of spinel ferrite formation. Field emission scanning electron microscopy (FE-SEM), coupled with energy-dispersive X-ray spectroscopy (EDS), provided insights into the morphology, stoichiometric and uniform distribution of ferrites within the polymer matrix. FTIR of the composite revealed the formation of the metastable ferroelectric phase of nylon 11. Finally, magnetic and dielectric properties of the composite were evaluated across varying ferrite concentrations.