This study was carried out to investigate the effect and the role of nitrogen-fixing nodules induced by Frankia bacteria on roots growth of Casuarina  glauca Sieber ex: Spreng plants in salinity tolerance and soil remediation. This study was carried out at the Experimental Station of Forestry and Wood Technology Department, Faculty of Agriculture, AlexandriaUniversity, Alexandria, and model nursery at Wadi EI- Natroon Region, Beheira Governorate, Egypt.  .  Three experiments were carried out as follows: Experiment 1: Eight NaCl concentrations (00.00 (S₁), 1000 (S₂), 3000 (S₃), 5000 (S₄), 7000 (S₅), 10.000 (S₆), 12.000 (S₇) and 14.000 ppm (S₈))  amended to root rhizosphere to pinpoint the maximum salinity level at which 50% of nodulated and unnodulated plants can survive. Experiment 2: In this experimentsplit-root technique was applied using double-container foam pots. Experiment 3: This experiment was conducted to study the effect of nodule diameter on salt tolerance and growth of the host and remediation of saline soil. In the first experiment, it was found that the nodulated plants had higher salinity tolerance than that of unnodulated ones. However, nodulated plants showed 40% survival at S₇, while unnodulated plant reached this survival percent at S₆. It was noticed that the growth rate of nodulated plants was significantly higher than that of unnodulated ones at S₄ up S₈. In the second experiment, it was noticed that unnodulated plants displayed the lowest survival (20 and 30% in first and second season, respectively). Shoot live ratio (SLR) of nodulated root under salinity stress was higher than that of unnodulated ones. However the reaction of nodules to direct salinization as well as the changes of characters of plants bearing it will be described and discussed in details.  The results of experiment 3 revealed the direct relationships between nodule diameter and N content of branchlets and total dry matter under salinity stress. On the other hand, it was found that the higher the nodule diameter, the lower the EC, Na, Cl contents in the rhizosphere obtained. Ultrastrastructural studies of nodules using SEM supported the foregoing results, since the filamentous hyphae of Frankia that colonized nodule cortex became finer and more condensed due to salinity stress. This modification brought forth an increase in surface area of filamentous hyphae to be adapted with saline rhizosphere.