Abstract <p>Drought stress represents an immense global environmental challenge, disturbing plant growth and survival. Thiamine and salicylic acid (SA) have been frequently exhibited to boost drought tolerance in plants, but their precise role in improving citrus resistance to drought stress remains unclear. The current study assessed the effect of different treatments of thiamine (0, 50, and 100 µM) and SA (0, 10, and 20 µM) on drought stress (5% PEG) in three important citrus rootstocks, ‘sour orange’, ‘volcamariana’, and ‘lime’, under in vitro conditions. Results revealed that drought stress negatively altered citrus growth and performance; however, the supplementation of thiamine and SA, particularly at 100 and 20 µM, respectively, modulated these adverse effects, with variable responses among the tested rootstocks. Notably, thiamine and SA promoted the germination percentage as well as several growth parameters, including shoot length, root length, leaf area, fresh weight, dry weight, and water content. Moreover, thiamine and SA modulated the negative effect induced by PEG through increasing chlorophyll <i>a</i>, chlorophyll <i>b</i>, and carotenoids and regulating proline and phenolic levels. The activities of antioxidant enzymes i.e., PAL, PPO, CAT, and POD were also modified by thiamine and SA, resulting in an activation of defensive machinery against drought stress. This framework provides a valuable strategy for the development of citrus adaptation in three rootstocks to drought stress, highlighting the contribution role of thiamine and SA in achieving sustainability in water-limited environments.</p>