In order to investigate the effect of irrigation levels, humic, and salicylic acid on some morphophysiological traits and sunflower yield, an experiment was conducted as a split-factorial design based on randomized complete block design with three replications at the research farm of Islamic Azad University, Birjand Branch. In this study, irrigation was considered as the main factor at two levels (120 and 240 mm pan evaporation), humic acid at three levels (0, 20, and 40 liters per hectare), and salicylic acid at two levels (0 and 0.75 mM) as sub-factors. Traits such as plant height, stem diameter, number of leaves per plant, head diameter, chlorophyll meter reading at flowering time, stomatal conductance at flowering time, seed yield, and seed water use efficiency were studied. The results showed that the effect of irrigation on plant height, head diameter, stomatal conductance, and seed yield was significant. The highest plant height (88 cm), head diameter (87.8 cm), stomatal conductance at flowering time (103.6 mmol m⁻² s⁻¹), and seed yield (1126.9 kg ha⁻¹) were obtained from the 120 mm pan evaporation irrigation level. The effect of salicylic acid on the chlorophyll meter reading at flowering time was significant, and the highest value was obtained in the control treatment (44). Based on the results of this research, to achieve maximum sunflower seed yield in the Birjand region, irrigation treatment after 120 mm cumulative pan evaporation, without the use of humic acid and salicylic acid, can be used.