Salinity is a significant threat to crop production in Oman and worldwide. Salt stress severely reduces plant productivity and yields. In Oman, the amount of cultivated land that is exposed to salinity is about 50%. Therefore, developing effective strategies for surviving with salinity and increasing plant's tolerance to salt stress is essential. The cowpea plant is considered an important grain legume because of its great nutritional value and ability to adapt to environmental stress like salinity. However, the cowpea loses its ability to grow and develop at a high salinity level. Proline is an amino acid that helps different crops tolerate salt and minimize the damage caused by salinity. Therefore, this study focuses on understanding proline's effect on cowpea plants exposed to salinity. The cowpea seeds were planted on soil and irrigated with different concentrations of NaCl (0, 40, 80, 100, and 150 mM) and proline solutions (0, 10, 20, 30, 60, and 80 mM) to evaluate the positive effect of proline on different levels of salinity by measuring changes in various plant's growth parameters. These measurements include plant height, leaf area, chlorophyll pigments, root system photosynthetic efficiency, and antioxidant defense integrity. Salinity negatively affects different morphological and photosynthetic parameters, such as the root system, chlorophyll pigments, and photosynthetic efficiency. In addition, it reduces a plant cell's capacity to absorb water and minerals and leads to ROS accumulation in cowpeas. However, the use of proline positively affected different morphological and photosynthetic parameters when the plants grew under control and saline conditions. For example, proline enhanced leaf area, plant height, chlorophyll pigments, photosynthetic efficiency, and antioxidant defense system. Additionally, proline showed a positive effect on the TPC, TFC, and glutathione when grown under saline conditions. Overall, the results showed that the cowpea plants treated with proline at a concentration of 30 mM were more tolerant to salt stress than the control. Furthermore, the results showed that cowpea plants had evolved effective antioxidant defense enzymes, including SOD, CAT, and APX to control oxidative damage under salt stress and proline conditions. This study is looking for a radical solution to the soil salinity issue and the role of proline in solving this problem to develop crops in Oman and the world.