The purpose of this study is to synthesize heavy nano-ferrites (e.g. nano-CaFe2O4 and nano-CuFe2O4) using facile and economical sol–gel method to investigate their effect on the physico-mechanical, morphological, and gamma radiation shielding of hardened cement pastes. After the synthesis process, the nano-ferrites were characterized using transmission electron microscopy (TEM), scanning electron microscopy/energy dispersive X-ray (SEM/EDX), X-ray diffraction (XRD) and particle size distribution analyses and then admixed to ordinary Portland cement (OPC) with different doses (e.g., 0, 0.25, 0.5, 1, and 2 mass%). The physico-mechanical characteristics of the cement pastes containing different ratios of heavy nano-materials were investigated at various hydration times. SEM/EDX and FTIR techniques were employed in addition to TGA/DTG to describe the microstructure and phase composition of the different hardened pastes. Gamma linear attenuation coefficients for Cs137 (662 keV) and Co60 (1173 and 1332 keV), as well as the most essential gamma transmission characteristics (half-value layer, HVL; tenth-value layer, TVL; and mean free path, MFP), were determined for selected pastes. The results revealed that the EDX spectrum of nano-CaFe2O4 clarifies that the Fe, Ca, and O elements are clearly observed at their corresponding keV values. Moreover, EDX spectrum of nano-CuFe2O4 properly reveals the presence of Cu, Fe, and O elements. These results confirm that the obtained product was of high purity. In addition, TEM photos indicate that the particle size of nano-CaFe2O4 is in the range of 7–22 nm, while the particle size range of nano-CuFe2O4 is 8–27 nm. It was found that the cement pastes containing 1% nano-CaFe2O4 and 1% nano-CuFe2O4 were the pastes that improved the physico-mechanical properties and high gamma ray shielding properties compared to the other prepared pastes. These nano-materials have high efficiency and economic feasibility.