Multimorbidity is common in older individuals and puts further strain on the burden of the health system. Particularly, cardiometabolic conditions and neurodegenerative disorders are prevalent in the aging population. However, the connection between cardiometabolic and neurocognitive health is not limited to later life. Accumulating evidence supports that neurodevelopmental and neurodegenerative processes share common mechanisms, and neurocognitive deterioration in later life may originate at the early-life stages. Cardiometabolic risk factors during the preconception period, pregnancy, and early life may influence neurodevelopment as well as later-life neurodegeneration. The underlying mechanisms are multifaceted, and a life course perspective is needed to identify targets for early intervention. In this chapter, we discuss biological (e.g., genetics and epigenetics), behavioral (e.g., diet, physical activity, smoking), and social (e.g., parental education, neighborhood environment) mechanisms underlying this connection and how they may contribute to the connection synergistically.