Brain disorders (e.g., stroke) often have cardiac causes. Cardiological diseases (e.g., heart failure) can lead to changes in brain function. Conversely, mental and neurological pathologies can affect the heart. Many systemic diseases and all vascular risk factors have cardiac and cerebral effects. This chapter discusses the most common cardiac causes of strokes, for example, atrial fibrillation and persistent foramen ovale. This is linked with rational recommendations for targeted diagnostics and therapy. In addition, changes in cognitive brain function, especially in the diseases atrial fibrillation and heart failure, are presented, as well as recommendations for the diagnosis and therapy of mental comorbidities (e.g., depression).