Glioblastoma multiforme is the most aggressive type of brain tumor with a strong ability to invade and migrate into surrounding normal brain tissues, leading to high tumor recurrence and mortality. Most of class-3 semaphorins, especially SEMA3A, SEMA3B and SEMA3F, have been reported to have strong tumor inhibition ability, but the role of SEMA3G in tumor biology is largely unknown. We report here that SEMA3G possesses anti-migration and anti-invasion ability. To determine the potential effects of SEMA3G on migratory and invasive ability, we generated stable SEMA3G expression U251MG cells. We found that stably overexpressed SEMA3G inhibited the migratory and invasive behavior of U251MG cells. In addition, treatment with SEMA3G conditioned media also decreased the migratory and invasive ability of parental U251MG cells. Furthermore, SEMA3G also inhibited the activity of MMP2, an index of tumor invasion ability. Thus, our results suggest that SEMA3G inhibited tumor cell migration and invasion, which may be obtained through cell autonomous or paracrine mechanisms, and SEMA3G is a potential target for antitumor migration and invasion.