Abstract <p>Soil heavy metal contamination presents a significant environmental challenge, necessitating the development of in-situ techniques to mitigate crop heavy metal accumulation. While exogenous abscisic acid (ABA) has been demonstrated to regulate the accumulation of individual heavy metals in plants, its concentration-dependent effects on different metals and its influence under combined heavy metal stress remain unclear. Our study reveals that exogenous ABA at concentrations ranging from 0.2 to 1 μmol L^–1 effectively reduces the accumulation of Ni, Zn, and Cd in <i>Arabidopsis</i> under single-metal stress, enhancing plant growth, with the optimal concentration being 0.4 μmol L^–1. At this concentration, the accumulation of Ni, Zn, and Cd in the shoots and roots decreased by 58 and 56%, 29 and 35%, and 50 and 35%, respectively. However, under single Pb stress, exogenous ABA at 0.2 to 1 μmol L^–1 significantly increased Pb accumulation in both roots and shoots. Further investigation indicates that exogenous ABA can concurrently inhibit Ni, Zn, and Cd accumulation in shoots and roots under combined heavy metal stress, with the most pronounced effect observed for Ni. Nonetheless, ABA fails to minimize Pb accumulation within the plant. In conclusion, exogenous ABA shows promising potential in regulating plant growth and Ni, Zn, and Cd accumulation under combined heavy metal stress conditions.</p>