Salinity and reducing its destructive effects on plant, soil, and water is among the most important challenges in agricultural lands. This study aims to evaluate the effect of zinc (Zn) and salinity on some physiological and biochemical properties of rosemary. A greenhouse experiment with two levels of Zn (0 and 20 mg kg−1) and salinity of sodium chloride (0, 60, and 120 mM) in a completely randomized design was used. Salinity decreased dry weight and concentrations of K, Ca, Mg, and Zn in rosemary shoots. However, it increased electrolyte leakage, shoot sodium concentration, phenolic compounds, and catalase activity. Zinc application increased rosemary dry weight by 13% and 9% under salinity levels of 0 and 60 mM NaCl, respectively. However, at higher salinity level (120 mM), it could not ameliorate the negative impact of salinity. Zinc improved the growth of rosemary under salinity stress by increasing the cell membrane stability, increasing shoot K, Ca, Mg, and Zn concentrations, and decreasing shoot Na concentration. The concentration of phenolic compounds in the leaves of rosemary grown under the salinity levels of 0 and 60 mM NaCl increased under the influence of Zn application. Nevertheless, the phenolic content remained unchanged under 120 mM NaCl salinity level. In this study, Zn addition increased catalase activity under all salinity levels. According to the results, optimum soil Zn application can be considered as an efficient and rapid solution for increasing rosemary growth and its tolerance to salinity stress.