<p>This study investigates the effect of phosphogypsum (PG) amendment on <i>Phoenix dactylifera</i> L. grown under saline conditions, aiming to improve growth and alleviate salt stress. Different PG doses (0, 10, 20, 30, and 40%) were applied to evaluate their effects on soil physicochemical properties and plant morphological, physiological, and biochemical traits. The incorporation of PG improved soil quality by neutralizing pH, increasing essential nutrients such as phosphorus, calcium, and potassium, and reducing electrical conductivity, which collectively enhanced plant mineral nutrition. Moderate PG doses (10–20%) significantly stimulated plant growth, with stem length increasing by 23.44%, leaf number by 44.44%, and stem diameter by 38.14%. These improvements were accompanied by higher chlorophyll content and favorable morphological parameters. Physiologically, moderate doses reduced oxidative stress markers, including malondialdehyde (MDA) and hydrogen peroxide (H₂O₂), and maintained enzymatic activities similar to control plants, indicating efficient stress management. Osmolyte analysis revealed increased soluble sugars in leaves, while proline decreased with higher PG doses, suggesting a differential adaptation strategy depending on the osmolyte. In contrast, higher doses of PG (≥ 30%) led to elevated oxidative stress, enzyme inhibition, and ionic imbalance, negatively affecting plant growth. These findings emphasize the necessity of optimizing PG application in saline soils. Overall, moderate PG doses (10–20%) enhance growth, nutrient status, and stress tolerance of date palms, while excessive doses compromise plant health and physiological functions. These results provide practical advice on the management of saline soils and sustainable cultivation of date palms in arid and semi-arid regions.</p> Graphical Abstract <p></p>