BaxCo1‐xFe12O19 (x = 0.2, 0.4, 0.6, & 0.8) nanoparticles are prepared via hydrothermal method. The hexagonal structure of x = 0.2 – 0.8 samples is confirmed by X‐ray diffraction patterns. Morphology indicated the existence of nanospheres like grains. The magnetic and dielectric parameters are clearly discussed as a function of composition at room temperature. The increase of Ba‐content reduced the magnetization from 56.1 to 49.7 emu g−1, and at higher Ba‐content, it is increased from 49.7 to 57.3 emu g−1. The x = 0.6 content offered the high ε' ≈9.54 and low ε" ≈0.12 values suitable for charge storage, and low noise device applications. Further, the thermal properties (using thermogravimetry (TG)‐differential thermogravimetry (DTG) & TG‐differential scanning calorimetry (DSC)) are elucidated in detail.