Loss of ARID1A has been reported to drive the progression of lung adenocarcinoma, yet the underlying mechanism remains elusive. In this study, we performed secretome analysis to identify the key secreted proteins regulating lung adenocarcinoma progression. We showed that the VASN level was significantly elevated in the conditioned medium from ARID1A-depleted A549 and H1299 cells. Restoration of ARID1A in ARID1A-depleted lung adenocarcinoma cells prevented the upregulation and secretion of VASN. Clinical analysis demonstrated a negative correlation between ARID1A and VASN expression in ARID1A-mutated lung adenocarcinomas. The patients with ARID1A-mutated lung adenocarcinoma had significantly higher concentrations of serum VASN than healthy controls. Moreover, serum VASN concentrations were associated with TNM stage, lymph node metastasis, and overall survival of the patients with ARID1A-mutated lung adenocarcinoma. Functional studies indicated that VASN overexpression potentiated the proliferation, invasion, and tumorigenesis of lung adenocarcinoma cells. Antibody neutralization of VASN suppressed the aggressiveness of ARID1A-depleted lung adenocarcinoma cells both in vitro and in vivo. Addition of recombinant VASN protein promoted the proliferation and invasion of lung adenocarcinoma cells. Additionally, knockdown of Notch1 blocked the aggressive phenotype induced by recombinant VASN protein. In conclusion, our data uncover the role of VASN in mediating the progression of ARID1A-depleted lung adenocarcinoma and highlight VASN as a promising therapeutic target for this disease.