Manganese-doped MnxFe3−xO4 (x = 0.0, 0.2, 0.6, 0.8) spinel ferrites were produced via co-precipitation using the ethanolamine. XRD results confirmed the formation of the spinel phase. The well-crystallized particles of the ferrite spinel phase had linear sizes in the range of 5–9 nm. It was found that the lattice parameter increases gradually as the Mn concentration is increased. XPS data supported the presence of Mn3+ and Mn4+ in the nanosized crystallites. A large specific surface area of 124–143 m2 g−1 was calculated using HRTEM and BET. The spontaneous magnetization increases monotonically from ∼51 emu g−1 for x = 0.0 up to ∼106 emu g−1 for x = 0.8. By contrast, the remanent magnetization changed non-monotonically from ∼3 emu g−1 for x = 0.0 up to ∼11 emu g−1 for x = 0.8, with a local maximum of ∼7 emu g−1 for x = 0.2 and a local minimum of ∼3 emu g−1 for x = 0.6. The coercivity also changed non-monotonically from ∼4 Oe for x = 0.0 up to ∼9 Oe for x = 0.8, with a minimum of ∼1 Oe for x = 0.2. The ordered magnetic moments for each sub-lattice were computed. The large values of the specific surface area indicate that the samples are good candidates for chemical and biological applications. The FT-IR and Raman spectra obtained supported the Rietveld refinement of XRD without forming any impurity phases. With an increase in the Mn concentration, magnetic investigations indicated an enhancement in the magnetic parameters of the obtained nanostructured samples.