Understanding the complex nature of reactive oxygen species (ROS) requires the development of new analytical techniques that are rapid, sensitive, and capable of real-time detection of both intra- and extracellular ROS. In this regards, electrochemical techniques have shown to be promising when compared to conventional techniques used for ROS studies. The broad applicability of electrochemical techniques in quantifying ROS in living cells has resulted in the development of a wide range of electrochemical ROS sensors to date. However, relatively few of them have found applications in real biological studies; most have remained at the proof-of-concept stage. Hybrid optoelectrochemical approaches such as scanning electrochemical microscopy and fluorescence microscopy have shown to augment the detection capabilities of electrochemical techniques, rendering them suitable for studying complex biological systems.