Toxoplasma gondii (T. gondii) is an obligate intracellular protozoan parasite. It has extensive host populations and is prevalent globally; T. gondii infection can cause a zoonotic parasitic disease. Microneme protein 3 (MIC3) is a secreted protein that is expressed in all stages of the T. gondii life cycle. It has strong immunoreactivity and plays an important role in the recognition, adhesion and invasion of host cells by T. gondii. This article reviews the molecular structure of MIC3, its role in the invasion of host cells by parasites, its relationship with parasite virulence, and its induction of immune protection to lay a solid foundation for an in-depth study of potential diagnostic agents and vaccines for preventing toxoplasmosis.