The effect of Yttrium Substitution on Co0.5Ni0.5YxFe2- xO4 (0.0 ≤ x ≤ 1.0) Ferrites as Microwave Absorbers was investigated to include structural, magnetic, dielectric and X-band absorption properties. The main objective of this work is to enhance microwave absorption properties of materials with interesting dielectric/magnetic behaviors by doping rare earth element of Yttrium based on transition metals. The hydrothermal method was used to create Yttrium (Y) substituted nanoparticles, and the effects of Y-ion substitution on the characteristics, structural, magnetic features were examined by XRD, FT-IR, SEM-EDS, TEM-SAED, and VSM, respectively. Electromagnetic properties were obtained from microwave scattering parameters measured via a metal-backed transmission line and Nicholson-Ross Weir techniques using a vector network analyzer (VNA) in conjunction with an X-band waveguide set. Return loss (RL) values of the samples were obtained from the electromagnetic constitutive parameters (permittivity and permeability). According to the XRD measurements, hexagonal crystal structure of ferrite and YFeO3 as secondary phase nanocrystal sizes are between 11 and 67 nm. Refined structural parameters using Rietveld analysis are carried out using the TOPAS refinement program. A good match was observed between the diffraction patterns obtained and calculated by Rietveld analysis. Moreover, the morphological analyses indicate that the relatively small spherical structures of Ni-Co ferrites particles can be seen to change from spherical to hexagonal-shaped with increasing yttrium concentration. The results of the FT-IR study show that the spinel structure has formed as predicted because the expected range of absorption bands is present. According to magnetic measurements, the coercivity (Hc) results show a modest increase in porosity as the Y-content rises. The results revealed that the minimum RL value and bandwidth vary significantly with the amount of Yttrium in the mixture, indicating that the obtained structures will be useful for broadband microwave applications.