Glioblastoma (GBM) is known as the most aggressive brain tumor and is characterized by a high heterogeneity and a median patient survival time around 15 months. Phenotyping based on cell mechanics is increasingly recognized as a potential prognostic marker for tumor aggressiveness. We have previously shown that cell and nuclear mechanical properties vary between different grades of gliomas and may be used to differentiate between GBM of different aggressiveness. Here, we find that the levels of lamin proteins can serve as an indicator of GBM aggressiveness. In patient-derived GBM cell lines, we found that cells from different GBM express different lamin levels. Nuclear size correlates positively with the ratio between lamin A and lamin B1 while nuclear stiffness increases with the levels of both lamin A and lamin B1. A simple mechanical model suggests that lamin A and lamin B1 act like springs in series. We also show that cells proliferate faster in GBM cell lines expressing higher lamin A levels. Downregulating lamin A expression in these cells reverse the aggressive phenotype. In contrast with breast cancer cells for which reduced lamin A levels favor cell migration in a confined environment, increased levels of lamin A may facilitate the invasion of more aggressive GBM cell lines in the soft environment of the brain. Furthermore, since nuclear deformation is a hallmark of malignancy in cancer cells, our results suggest that nuclear shape and mechanics may serve as prognosis biomarkers for GBM.