The REV-ERB nuclear receptors are key components of the circadian clock. Loss of REV-ERBs in the mouse heart causes dilated cardiomyopathy and premature lethality. This is associated with a marked reduction in NAD+ production, but whether this plays a role in the pathophysiology of this heart failure model is not known. Here, we show that supplementation with the NAD+ precursor NR as a dietary supplement improves heart function and extends the lifespan of female mice lacking cardiac REV-ERBs. Thus, boosting NAD+ levels can improve cardiac function in a setting of heart failure caused by disruption of circadian clock factors, providing new insights into the links between the circadian clock, energy metabolism, and cardiac function.