Abstract Objective To analyze the Prolyl 4-Hydroxylase subunit Alpha-2 (P4HA2) expression in Lung Adenocarcinoma (LAUD). Methods The authors assessed P4HA2 expression in the LUAD tumor ecosystem using single-cell analysis. The authors analyzed the relationship between P4HA2 expression and clinical features in LUAD and Brain Metastasis (BM) cases. The authors assessed the biological functions of P4HA2 using The Cancer Genome Atlas-LUAD dataset. Results P4HA2 was more highly expressed in fibroblasts than in epithelial cells in normal lung and lung adenocarcinoma tissues (p < 0.001). P4HA2 was more highly expressed in malignant epithelial cells than in fibroblasts in the BM tissue (p = 0.002). P4HA2 expression was significantly higher in female cases than in male cases (p = 0.049) and was related to lymph node metastasis (p = 0.019) and a higher TNM stage (p = 0.020). High P4HA2 expression indicated a poor prognosis and served as an independent prognostic risk factor in lung cancer. P4HA2 was mainly enriched in the extracellular matrix organization, NADH regeneration, and canonical glycolysis. P4HA2 expression was negatively correlated with naive B cells, T-cells, CD8, and activated natural killer cells, but positively correlated with CD4 memory-activated T cells, regulatory T-cells, resting dendritic cells, and dendritic cell activation. P4HA2 messenger RNA expression was correlated with programmed death-ligand 1 and cytotoxic T-lymphocyte-associated protein 4. Conclusion P4HA2 is highly expressed in LUAD tumor cells, especially for the BM subtype, and is a valuable prognostic indicator of LUAD. It may be involved in a biological activity of distant metastasis of LUAD tumor cells and serve as a potential treatment target.