The effect of drought stress on 3-leaf stage (V2) maize (Zea mays L.) seedlings over-expressing or down-regulating the Zea mays phytoglobin 1 gene (ZmPgb1) was investigated using applications of 25% w/v polyethylene glycol (PEG) to mimic drought. Over-expression of ZmPgb1 increased drought tolerance, decreased wilting, and decreased the accumulation of ethylene and reactive oxygen species (ROS), compared to wild type (WT) plants and plants in which the level of ZmPgb1 was down-regulated. Gene expression studies conducted during the first 16 hours of water stress revealed a transcriptional induction of ethylene synthesis and response, as well as ROS production, in the ZmPgb1 down-regulating plants relative to WT plants. This was in contrast to the ZmPgb1 over-expressing plants where genes participating in ethylene synthesis and response exhibited the lowest expression levels, and ROS production was also limited. Based on these results, a model is proposed in which suppression of NO signalling by ZmPgb1 reduces ethylene accumulation and response, and production of ROS, which are conditions alleviating drought stress.