Background: Primary glioblastoma is characterized by an extremely poor prognosis. The promoter methylation ofGATA4leads to the loss of its expression in many cancer types. The formation of high-grade astrocytomas can be promoted by the concurrent loss ofTP53and GATA4 in normal human astrocytes. Nevertheless, the impact ofGATA4alterations with linkage toTP53changes in gliomagenesis is poorly understood. This study aimed to evaluate GATA4 protein expression,GATA4promoter methylation, p53 expression,TP53promoter methylation, and mutation status in patients with primary glioblastoma and to assess the possible prognostic impact of these alterations on overall survival. Materials and Methods: Thirty-one patients with primary glioblastoma were included. GATA4 and p53 expressions were determined immunohistochemically, andGATA4andTP53promoter methylations were analyzed via methylation-specific PCR.TP53mutations were investigated via Sanger sequencing. Results: The prognostic value of GATA4 depends on p53 expression. Patients without GATA4 protein expression were more frequently negative forTP53mutations and had better prognoses than the GATA4 positive patients. In patients positive for GATA4 protein expression, p53 expression was associated with the worst outcome. However, in patients positive for p53 expression, the loss of GATA4 protein expression seemed to be associated with improved prognosis.GATA4promoter methylation was not associated with a lack of GATA4 protein expression. Conclusions: Our data indicate that there is a possibility that GATA4 could function as a prognostic factor in glioblastoma patients, but in connection with p53 expression. A lack of GATA4 expression is not dependent onGATA4promoter methylation. GATA4 alone has no influence on survival time in glioblastoma patients.