The BT/NZFO composite ceramics derived by sol–gel in situ process were successfully prepared. The phase composition, morphology, and microstructure of the composite ceramics were determined and observed by X-ray diffractometer (XRD), SEM, and EDS. Results showed that the Ni–Zn ferrite (NZFO) phase started to grow initially and then the BaTiO3 (BTO) phase grew among the interfaces of NZFO particles at high ferrite content. The observation of microstructure showed that the NZFO phase in large grain size is enwrapped by the BTO phase in small grain size, and the constituent phases existed in the form of solid solutions doped with Fe and Ti, respectively. The densification and microstructure depended on the volume fraction of ferrite (fNZFO). The appropriate sintering temperature was 1280°C–1300°C at which stable phase structure could be obtained for the BTO/NZFO composite. The maximum permittivity could achieve 86 000, and the initial permeability was as high as 162 when the ceramics was loaded with 95% ferrite and sintered at 1300°C for 12 h. The BT/NZFO composite ceramics exhibited impressive dielectric and magnetic properties, making it a potential candidate for wide applications in the integration of electronic devices.