A bimagnetic nanostructure was designed where the antiferromagnetic  (AFM) NiO nanoparticles (NPs) are confined within the pores of a mesoporous ferrimagnetic (FiM) CoFe₂O₄ matrix. An amount of 3.4 wt % of 9 ± 1 nm NiO NPs was inserted into pores of 35 ± 5 nm clustered CoFe₂O₄ NPs when the −NH3+ groups of cysteamine on the NiO NP surface electrostatically bind to the −OSO₃⁻ of sodium dodecyl sulfate (SDS) attached to CoFe₂O₄ NPs. The role of in situ embedded NiONPs is 3-fold: (i) to nearly double the saturation magnetization (M_S) and coercivity (HC) by suppressing the frozen disordered spins on the surface of CoFe₂O₄ NPs surrounding the NiO NPs inside the pores at the cost of enhanced FiM ordering, (ii) to introduce AFM/FiM exchange coupling by breaking the spin glass surface layer to provide exchange bias (EB) of 233.0 ± 0.2 Oe at 5 K with a cooling field of 2 T, and (iii) to provide symmetry to the asymmetric nature of the hysteresis loop of CoFe₂O₄. In the absence of cooling field, the pristine CoFe₂O₄ NP porous matrix shows hysteresis loop shifts of >1000 Oe and asymmetric magnetization reversal which are uncommon in spinel oxides.