Nanobiotechnology approaches to engineering crops with enhanced stress tolerance may be a safe and sustainable strategy to increase crop yield. Under stress conditions, cellular redox homeostasis is disturbed, resulting in the over-accumulation of reactive oxygen species (ROS) that damage biomolecules (lipids, proteins and DNA) and inhibit crop growth and yield. Delivering ROS-scavenging nanomaterials to plants has been shown to alleviate abiotic stress. Here we review the current state of knowledge of using ROS-scavenging nanomaterials to enhance plant stress tolerance. When present below a threshold level, ROS can mediate redox signalling and defence pathways that foster plant acclimatization against stress. We find that ROS-triggering nanomaterials, such as nanoparticulate silver and copper oxide, have the potential to be judiciously applied to crop species to stimulate the defence system, prime stress responses and subsequently increase the stress resistance of crops.