HEAVY metal toxicity is one of the major abiotic stresses leading to inhibition of growth and yield of plants. Aluminum (Al³⁺) treatment resulted in a significant decrease in the fresh and dry biomasses of shoots and roots as well as leaf relative water content (RWC) of lupin plants. This reduction was associated with a significant decrease in IAA and GA₃ contents and increase in ABA level. Furthermore, increasing Al³⁺ levels induced generation and accumulation of H₂O₂ and MDA in shoots and roots of lupin plants. The enhancement of oxidative stress was associated with biosynthesis of non-enzymatic antioxidants including proline, phenolics and trigonilline components together with an increase of G6PDH activity and NADP⁺/NADPH ratio. In addition, Al³⁺ stress triggered an increase in antioxidant enzymes SOD and CAT, whereas GPx, PPO, GR, and APx activities were markedly suppressed. Priming treatment of lupin seeds with salicylic acid could considerably reverse the Al3+-induced inhibitory effects via induction of defense mechanisms and increase growth regulator contents.