Chitosan and its components have beneficial effects on a wide variety of plant species. Yet, their effects on wheat plants under drought stress are not well known. So, a field experiment was laid out in order to evaluate the effect of chitosan nanoparticles (NPs) on wheat. The wheat seeds were sown in plots. Then, the chitosan NPs were added to them through soil and foliar application at tillering, stem elongation, and heading stages. Results indicated that the drought stress significantly decreased majority of the studied traits compared to the normal irrigation. Application of the NPs especially 90 ppm increased leaf area (LA), relative water content (RWC), chlorophyll content, photosynthesis rate, catalase (CAT), and superoxide dismutase (SOD) activities, yield, and biomass compared to the control. Finally, our results highlight that usage of the chitosan NPs especially 90 ppm can mitigate adverse effects of drought in the wheat under drought stress.