Water deficiency poses a significant challenge to global agricultural systems, impacting crop performance and product quality. Compounds like putrescine have demonstrated the potential to enhance plant resilience to environmental stresses. This pot study, conducted in 2023 at Imam Khomeini International University, Ghazvin, Iran, employed a factorial experiment based on a completely randomized design with three replications, aimed to assess the impact of varied irrigation levels and foliar application of putrescine on both quantitative and qualitative traits of holy basil (Ocimum sanctum L.). Water deficiency was induced at three levels (100, 75, and 50% of Field Capacity), and putrescine foliar spray was applied at concentrations of 0, 0.1, and 0.2 mM. Results indicated that water scarcity significantly reduced plant growth indices, Relative Water Content (RWC), and photosynthetic pigment levels. However, foliar spray with putrescine effectively mitigated these adverse effects. Furthermore, the combination of water deficiency and the application of 0.2 mM putrescine increased total phenolic compounds (48.76%), flavonoid compounds (54.85%), and restrained free radical DPPH (44.85%) compared to the control. Putrescine-treated plants exhibited a noteworthy increase in essential oil percentage compared to the control group. Furthermore, as water deficiency increased, the essential oil composition also increased the percentages of 1,8-cineole and methyl eugenol compared to the control plants. In conclusion, foliar application of putrescine resulted in a significant enhancement in the essential oil's key compounds in holy basil.