Brain natriuretic peptide (BNP) release is a marker of increased myocardial wall tension, which is elevated in patients with disturbed left ventricular function. As it is increasingly being used as a reliable marker for diagnosis, optimization of pharmacological treatment, and risk stratification, BNP measurement might be also relevant for patients undergoing cardiac surgery. Measured BNP levels can be used to predict postoperative complications and the risk of further cardiac events. Preoperative BNP levels support the decision for the timing of aortic valve replacement in asymptomatic severe aortic stenosis. An increase in BNP levels early predicts allograft rejection after cardiac transplantation or ineffective cardiac resynchronization therapy. Moreover, BNP levels can be used to differentiate between cardiac and non-cardiac reasons for acute dyspnea in the management of surgical patients. Finally, the application of recombinant human BNP seems to improve recovery after cardiac surgical procedures. Thus, BNP can be a helpful tool for monitoring and treating patients before, during, and after cardiac surgery to predict and improve the effectiveness of therapy and reduce hospitalization and costs.