Renal dysfunction (RD) in heart failure portends adverse outcomes and often limits aggressive medical and decongestive therapies. Despite the high prevalence in this population, not all forms of RD are prognostically or mechanistically equivalent: RD can result from irreversible nephron loss secondary to diabetic or hypertensive kidney disease or it can develop secondary to heart failure (HF) itself, i.e., the cardiorenal syndrome. Furthermore, filtration is only one aspect of renal performance such that significant renal impairment secondary to cardiorenal syndrome can exist despite a normal glomerular filtration rate. Renal biomarkers have the potential to inform some of the intricacies involved in accurately assessing cardiorenal interactions. This article discusses novel biomarkers for cardiorenal syndrome and their utility in the prognosis, diagnosis, and targeted treatment of heart failure-induced RD.