Sickle cell disease (SCD) is a hereditary blood disorder affecting millions of people in which red blood cells (RBCs) become sickled and lyse easily driven by polymerization of hemoglobin. Chronically, SCD causes anemia and biventricular dysfunction. GBT440 is an experimental treatment for SCD that prevents hemoglobin polymerization. We hypothesized that 17-month-old Berkeley SCD mice treated with GBT440 would have increased hematocrit (Hct) and better biventricular function compared to vehicle treated SCD mice. Our results demonstrate that 3 weeks of GBT440 treatment eliminated chronic anemia, increased left ventricular ejection fraction (LVEF) and stroke volume index, and improved right ventricular function. Overall, our findings support a therapeutic effect of GBT440 in vivo in a small animal model of SCD. Next steps in investigating mechanisms of improved cardiac function are warranted.