Nitric oxide (NO) is a molecule of vast physiological significance, but much remains unknown about the in vivo concentration dependence of its activity, its basal level concentrations, and how levels fluctuate in the course of certain disease states. Although electrochemical methods are best suited to real-time, continuous monitoring of NO, sensors must be appropriately modified to ensure adequate selectivity, sensitivity, sensocompatibility, and biocompatibility in challenging biological environments. Herein, we provide a critical overview of recent advances in the field of electrochemical NO sensors designed to operate in physiological milieu. Unique to this review, we have opted to highlight research efforts undertaking meticulous characterization of the sensor's analytical performance. Furthermore, we compile basic recommendations to inform future electrochemical NO sensor development and facilitate cross-comparison of proposed sensor designs.