Salvia officinalis, commonly known as sage, is a medicinal plant valued for its therapeutic properties. This study investigates the effects of salt stress on S. officinalis L., focusing on its vegetative growth, and photosynthetic performance under varying salinity levels (5, 25,50, 100, 150, and 200 mM) and the duration of exposure. Salt stress significantly reduced shoot length, leaf relative water content (RWC), and overall plant growth, primarily due to decreased soil water potential, ion toxicity, and disrupted nutrient balance. Prolonged exposure to high salinity further impaired cell division and elongation, exacerbating growth inhibition. Photosynthetic efficiency (PN) declined under salt stress, with short-term exposure causing rapid but temporary reductions, while long-term exposure led to sustained decreases driven by stomatal limitations (reduced stomatal conductance, Gs, and transpiration rate, E) and non-stomatal factors such as toxic ion accumulation and reduced enzymatic activity. The study highlights the role of water-use efficiency (WUE) in mitigating salt stress, as sage seedlings accumulated compatible solutes to maintain osmotic balance and sustain photosynthesis. This adaptive mechanism enabled plants to reduce water loss and cope with ion toxicity, enhancing resilience to salinity. However, physiological responses were strongly influenced by both the intensity and duration of salt exposure, with higher concentrations and prolonged stress amplifying negative effects. These findings underscore the complex interplay of osmotic, ionic, and photosynthetic adjustments in S. officinalis under salt stress, providing insights into its adaptive strategies and limitations in saline environments. To deepen our understanding of how plants tolerate salt stress and to develop strategies for enhancing crop resilience, it is essential to conduct further research that quantifies the accumulation of compatible solutes—such as proline, sugars, and organic acids—in leaves subjected to saline conditions. These solutes play a crucial role in mitigating the adverse effects of salt stress.