Lung adenocarcinoma (LUAD) is the most common form of lung cancer and a leading cause of cancer-related mortality, underscoring the need for new chemopreventive strategies. α-Ketoglutarate (α-KG), a tricarboxylic acid cycle metabolite and dioxygenase cofactor, links cellular metabolism to chromatin regulation. Here, we show that dietary α-KG remodels LUAD in a sex-dependent manner. In female mice, α-KG reduced tumor area, decreased repressive histone marks (H3K27me3, H3K9me3), and upregulated TBX5 and myogenesis-associated genes. In male mice, α-KG-treated male mice exhibited increased tumor area, elevated H3K27me3, and immune remodeling characterized by CD8⁺ T cell expansion and transcriptomic signatures of T cell exhaustion. Analysis of human LUAD revealed that TBX5 expression is enriched in female tumors and associated with improved survival, suggesting it may serve as a marker of favorable outcome. Together, these findings support α-KG as an epigenetic modulator with potential chemopreventive activity in lung cancer and highlight the importance of incorporating sex as a biological variable in preclinical studies.