Nitrous oxide (N₂O) is a potent greenhouse gas, contributing to global warming. Most of the N₂O emitted from cropping systems is derived from the soil and is closely related to the use of nitrogen (N) fertiliser. However, several reports have shown that small, yet significant, portions of the N₂O flux from cropping systems are emitted from the crop foliage. This research aimed to quantify N₂O emissions from the foliage of field-grown cotton (Gossypium hirsutum L.), and included maize (Zea mays L.) and soybean (Glycine max L.) for comparison. We also aimed to identify differences in the timing of N₂O emissions from foliage during the day and over an irrigation cycle. Individual plants were isolated from the soil, and the atmosphere surrounding the encapsulated plants was sampled over a 30-min period. Subplots that were previously fertilised with urea at 0, 80, 160, 240 and 320 kg N ha^–1 and then sown to cotton were used to measure N₂O flux from plants on three occasions. N₂O flux from cotton foliage was also measured on five occasions during an 11-day irrigation cycle and at five times throughout one day. N₂O flux from foliage accounted for a small but significant portion (13–17%) of the soil–crop N₂O flux. N₂O flux from foliage varied with plant species, and the time of day the flux was measured. N₂O flux from cotton plants was closely related to soil water content. Importantly, the application of N fertiliser was not related to the N₂O flux from cotton plants. The most plausible explanation of our results is that a proportion of the N₂O that was evolved in the soil was transported through the plant via evapotranspiration, rather than being evolved within the plant. Studies that exclude N₂O emissions from crop foliage will significantly underestimate the N₂O flux from the system.