The expression of deoxythymidylate kinase (DTYMK) is up-regulated in liver cancer. However, the underlying biological function and potential mechanisms of DTYMK driving the progression of lung adenocarcinoma remains unclear. In this study, we investigated the role of DTYMK in lung adenocarcinoma and found that the expression of DTYMK in LUAD tissues was significantly higher than that of DTYMK expression in adjacent normal tissues. Kaplan-Meier survival analysis showed that patients with higher DTYMK expression correlated with adverse prognosis. ROC curve analysis showed that the AUC value of DTYMK was 0.914. Correlation analysis showed that DTYMK expression was associated with immune infiltration in LUAD. Finally, we determine that DTYMK regulated cell proliferation, cell migration, and cell cycle of lung adenocarcinoma in vitro. In conclusion, our data demonstrated that DTYMK was correlated with progression and immune infiltration, and could serve as a prognostic biomarker for lung adenocarcinoma.