This study attempted to research the molecular mechanism underlying the inhibitory role of miR-1225-5p in the malignant progression of glioblastoma. Bioinformatics analyses based on the gene expression omnibus (GEO) and Chinese glioma genome atlas (CGGA) databases showed that miR-1225-5p, as a favorable prognostic factor, was expressed at low levels in glioblastoma, and its expression was also related to WHO grade and age. The subsequent CCK-8 assay indicated that miR-1225-5p might prevent the malignant progression of glioblastoma, which was represented by that miR-1225-5p mimic reduced the viability of glioblastoma cells. Then, we predicted that FNDC3B might be a potential target gene of miR-1225-5p, and it was negatively correlated with the level of miR-1225-5p, which were confirmed by dual-luciferase reporter assay, qRT-PCR and western blot assays. Moreover, based on the analyses of the cancer genome atlas (TCGA), Oncomine and CGGA databases, FNDC3B was enriched in glioblastoma and high expression of FNDC3B led to poor prognosis. Finally, CCK8 and transwell experiments showed that the ability of miR-1225-5p to inhibit glioblastoma cell viability, invasion and migration was at least partially achieved by targeting FNDC3B. In general, these results revealed that the miR-1225-5p/FNDC3B axis contributes to inhibiting the malignant phenotype of glioblastoma cells, which lays a foundation for molecular diagnosis and treatment of glioblastoma.