Lung cancer (LC) is the leading cause of death worldwide, and lung adenocarcinoma (LUAD) is the most common form of LC. The abnormally high expression of myelin protein zero-like 1 (MPZL1) promotes the malignant progression of various tumors. However, there is no relevant report on the functional role of MPZL1 in LUAU. In this study, we applied Illumina sequencing to screen differentially expressed genes. Subsequently, MPZL1 was selected as hub gene for quantitative real-time polymerase chain reaction (qRT-PCR) and CCK8 assay. The expression level of MPZL1 was analyzed by immunohistochemistry, immunofluorescence, western blot, and qRT-PCR. After silencing or overexpressing MPZL1, CCK8, EDU, clone formation, scratch healing, invasion, and nude mouse tumor-bearing experiments were performed to detect the abilities of cell proliferation, migration, invasion, and tumorigenicity. Moreover, qRT-PCR, western blot, coimmunoprecipitation, and scratch healing assays were conducted to explore the transcriptional regulatory factors of MPZL1. Finally, the relationship between MPZL1 and immunotherapy was explored through public databases and validated . The results show that a total of 196 high-expressed genes and 496 low-expressed genes were screened. Differential genes are mainly enriched in cell proliferation and division, protein binding, and other pathways and functions. MPZL1 was selected as the hub gene and upregulated in LUAD tissues and cells. Silencing MPZL1 inhibited the cell proliferation and cloning formation, and the growth of tumor. Conversely, overexpression of MPZL1 has the opposite effect. In addition, MPZL1 combines with the transforming growth factor-β1 to promote the progress of LUAD. Finally, we found that high expression of MPZL1 is negatively correlated with infiltration of CD8 cells and may lead to immunotherapy resistance. In summary, this study revealed a new mechanism by which MPZL1 promotes LUAD progression by enhancing tumor proliferation, invasion, migration, and suppressing immune function.