Aberrant activation of Wnt/β-catenin signaling and dysregulation of metabolism have been frequently observed in lung cancer. However, the molecular mechanism by which Wnt/β-catenin signaling is regulated and the link between Wnt/β-catenin signaling and cancer metabolism are not fully understood. In this study, we showed that the loss of dual serine/threonine tyrosine protein kinase (DSTYK) led to the activation of Wnt/β-catenin signaling and upregulation of its target gene, lactate dehydrogenase (LDHA), and thus the elevation of lactate. DSTYK phosphorylated the N-terminal domain of β-catenin and inhibited Wnt/β-catenin signaling, which led to the inhibition of cell growth, colony formation and tumorigenesis in a lung adenocarcinoma mouse model. DSTYK was downregulated in lung cancer tissues, and its expression was positively correlated with the survival of patients with lung adenocarcinoma. Taken together, these results demonstrate that the loss of DSTYK activates Wnt/β-catenin/LDHA signaling to promote the tumorigenesis of lung cancer and that DSTYK may be a therapeutic target.