P53 is a tumor protein that acts as a tumor suppressor. The mutation of P53 may cause loss of tumor suppressor functions and gain of functions favoring cellular proliferation and apoptosis inhibition. The clinical implications of the tumor protein P53 gene (TP53) mutation in lung adenocarcinoma are indefinite. The aim of this study is to explore the clinical significance of the mutant P53 protein expression in lung adenocarcinoma tissues.The clinicopathological data of 120 lung adenocarcinoma patients who underwent surgery were retrospectively analyzed. The mutant P53 protein expression was detected using the immunohistochemical method. Furthermore, the relationship between the mutant P53 expression and the clinicopathological parameters was analyzed using the Chi-square test, whereas that between the mutant P53 expression and overall survival was estimated using the Kaplan-Meier method and Cox regression model.The mutant P53 protein expression rate was 63.3%. Accordingly, the mutant P53 expression was significantly associated with tumor size (P=0.041) and clinicopathological stage (P=0.025). On the one hand, a univariate survival analysis showed that tumor size (P=0.031), lymph node metastasis (P<0.001), clinicopathological stage (P<0.001), and mutant P53 expression (P=0.038) were associated with overall survival. On the other hand, a multivariate survival analysis showed that lymph node metastasis (P=0.014) was an independent poor prognostic factor for overall survival.Patients with lung adenocarcinoma with mutant TP53 had a poor outcome. Accordingly, the mutant P53 protein may serve as a molecular prognosis marker for lung adenocarcinoma patients.