<p>Heavy metal (HM) stress, primarily driven by industrial and other anthropogenic activities, poses a serious threat to the environment and human health. Phytoremediation offers a sustainable, ecologically friendly, and cost-effective approach to mitigate pollutant diffusion. This study aimed to evaluate the effects of chromium (Cr), nickel (Ni), and lead (Pb) on the germination and early seedling growth of <i>Acacia saligna</i> (Labill.) H.L.Wendl., an ornamental tree native to Australia and now cultivated worldwide. Different concentrations (0, 200, 400, 600, 800, and 1000&#xa0;mg L^–1) of the aforementioned HMs were tested under controlled germination conditions. The results showed that <i>A. saligna</i> seeds were significantly more tolerant to Pb, with approximately 17% germination at 1000&#xa0;mg L^–1, compared to Cr and Ni, which completely inhibited germination at 800&#xa0;mg L^–1. Despite a general decline in seedling growth under HM stress, Ni treatment enhanced water absorption and biomass accumulation. HM treatments stimulated the accumulation of soluble proteins, proline, and catalase activity, with Cr stress uniquely inducing a significant (<i>p</i> &lt; 0.05; <i>Tukey</i>’s test) increase in soluble sugar synthesis. Interestingly, despite the high mobility of Pb in seedlings, the malondialdehyde (MDA) level was the lowest in the presence of this metal, suggesting the plant’s capacity for Pb chelation and neutralization. These findings indicate that <i>A. saligna</i> employs diverse adaptive mechanisms to survive in HM-contaminated soils, highlighting its potential for the phytoremediation of HM-polluted environments.</p>