Vitamins are indispensable micronutrients in dairy nutrition, influencing productivity, reproduction, and animal health. Despite their minute quantitative requirement, vitamins play critical roles as cofactors, antioxidants, and regulators of metabolic processes. In practical dairy rations, however, the efficiency of vitamin supplementation is influenced by rumen microbial activity, dietary composition, feed preservation, and management factors. This review critically examines the physiological importance of vitamins in dairy cows, evaluates the potentials of supplementation strategies for optimizing productivity and health, and identifies constraints limiting their efficacy under field conditions. An understanding of these dynamics enables evidence-based formulation of vitamin-inclusive rations that support sustainable dairy production systems.