A simplified, fast, and effective production method has been developed for the synthesis of manganese ferrite (MnFeO) magnetic nanoparticles (MNPs). In addition to the wide applicability of MnFeO MNPs, this work also reports their application in DNA isolation for the first time. An ultrasonic-cavitation-assisted combustion method was applied in the synthesis of MnFeO MNPs at different furnace temperatures (573 K, 623 K, 673 K, and 773 K) to optimize the particles' properties. It was shown that MnFeO nanoparticles synthesized at 573 K consist of a spinel phase only with adequate size and zeta potential distributions and superparamagnetic properties. It was also demonstrated that superparamagnetic manganese ferrite nanoparticles bind DNA in buffer with a high NaCl concentration (2.5 M), and the DNA desorbs from the MNPs by decreasing the NaCl concentration of the elution buffer. This resulted in a DNA yield comparable to that of commercial DNA extraction products. Both the DNA concentration measurements and electrophoresis confirmed that a high amount of isolated bacterial plasmid DNA (pDNA) with adequate purity can be extracted with MnFeO (573 K) nanoparticles by applying the DNA extraction method proposed in this article.