The introduction of instrumentation based on microfluidic technologies has revolutionised many areas of life sciences, including genomics and proteomics amongst others. As the role of reactive oxygen species has more recently been linked to an important number of pathologies, such as cancer or cardiovascular disease, this particular field of study has not been the exception in adopting these new technologies. Added interest has been generated thanks to the high compatibility of reactive oxygen species detection techniques in microfluidic devices and previously established ones e.g. fluorescence or electrochemistry. Moreover, innovation in the field has generated devices capable of detecting the state denominated oxidative stress (in vivo), produced by an unbalance between the production of reactive oxygen species and intrinsic antioxidant mechanisms, as well as assessing the capacity of other endogenous molecules to counter the harmful effects of these species. This review has focused on how miniaturisation enabled by microtechnologies and the understanding of microfluidics has offered researchers a unique insight into the cellular processes involving the production of reactive oxygen species in the cellular metabolism, as well as providing a tool for antioxidant capacity screening of compounds.