Among the possible substitutes for noble metals, cobalt-based catalysts represent promising alternative systems. In recent years, many articles have been devoted to the synthesis, characterization and reactivity of cobalt oxides. This article provides a comprehensive review of the state-of-the-art activities that concentrate on the synthesis, structural properties and catalytic applications of Co₃O₄ nanocrystals and Co₃O₄–MO_x binary oxides in CO, CH₄ and VOC oxidation at low temperatures. It begins with the major synthetic approaches and basic properties of Co₃O₄ nanocrystals and Co₃O₄–MO_x binary oxides and subsequently highlights the relationship between the peculiar structure of Co₃O₄ nanocrystals and their catalytic activity (or between the redox properties of Co₃O₄–MO_x binary oxides and their catalytic activity). Finally, the active sites and key factors determining the catalytic oxidation over Co₃O₄ and Co₃O₄–MO_x are discussed. The perspective with respect to future research on Co₃O₄ nanocrystals and Co₃O₄–MO_x binary oxides is considered.