Fluid management during cardiopulmonary bypass (CPB) is challenging, as inadequate volume leads to poor perfusion and ischemia to vital organs, while excessive volume causes hemodilution, fluid extravasation, tissue edema, and coagulopathy. Fluid management is a continuous process before, during, and after CPB. Fluid status at each stage must be carefully evaluated and managed with a holistic approach, not in isolation. This chapter discusses how to monitor fluid and end-organ perfusion status, choices of fluids in cardiac surgery, priming solutions, cardioplegia, reservoirs, circuits, acid–base and electrolyte management, blood pressure and pump flow controls, goal-directed fluid therapy, organ protection, CPB separation, and fluid management before and after CPB.