In an effort to help meet the demand for promising renewable sources of energy, research into innovative downstream processing for microalgae biorefineries is actively underway. In the current work, we used octahedrally shaped ZnFe2O4 nanoparticles for both harvesting and disrupting the cells of microalgae. We were able to use ZnFe2O4 octahedrons as magnetic flocculants and cell-disruption agents because ZnFe2O4 nanoparticles have both magnetic and photocatalytic properties. The ZnFe2O4 octahedrons, when simply functionalized with the aminosilane N-[3-(trimethoxysilyl)propyl] ethylenediamine, enabled a rapid and energy-efficient harvesting of microalgae. Furthermore, the ZnFe2O4 octahedrons, well-known for having photocatalytic properties superior to those of ZnFe2O4 nanoparticles with other morphologies, were used to lyse the algal cell wall with the aid of H2O2 under simulated sunlight irradiation. We expect microalgae whose cells can be both magnetophoretically separated and lysed by the same ZnFe2O4 nanoparticles to be utilized as bioenergy resources for more efficient downstream processing than is currently available.