Around parturition in dairy cows, the increased demand for nutrients to sustain fetal growth and lactation, coupled with depressed feed intake, impose tremendous metabolic stress. Consequently, the metabolic challenge and inflammation incurred during this period have been shown to lead to health problems and compromised lactation performance. Various nutrients are known to promote a smooth transition from gestation to lactation by fine-tuning immunometabolism. Methionine, an essential amino acid (AA) engaged in various key physiologic events, has been underscored as a limiting AA for milk protein synthesis. Apart from its apparent key role in mammary gland and liver protein synthesis, methionine also serves as a substrate for sulfur-containing antioxidants, namely glutathione and taurine. Additionally, as a key component of one-carbon metabolism, hundreds of methylation reactions acquire methyl groups from methionine via S-adenosyl methionine. Recent research has highlighted the milk production and health benefits from methionine supplementation during the transition period. This presentation will provide a brief review of the impact of methionine on transition dairy cow health and productivity as well as the underlying alterations in immunometabolism. Specifically, this presentation will discuss results from studies showing the role of methionine supplementation in inducing metabolic changes in (1) plasma AA profile and utilization; (2) liver and skeletal muscle metabolome; (3) hepatic sulfur-containing antioxidant pool and metabolism; and (4) hepatic one-carbon metabolism in vivo and in vitro. In the future, the opportunity and challenge will be to continue to improve our understanding of how functional nutrients affect immunometabolism in dairy cows and effectively apply this knowledge to feeding and management in the dairy industry.