Salinity has adverse effects on germination, emergence, growth, and yield of pepper plants, and effective strategies must be developed to overcome this issue. The study aimed to mitigate the negative effects of salinity stress on pepper plants by applying biochar. The pepper plants were grown in peat culture with varying levels of NaCl: 0% (no stress), 0.5% (moderate stress), and 1% (severe stress), combined with different biochar concentrations (0%, 2%, 4%, and 6%). After 30 days of exposure, the morphological and physiological properties of the pepper plants were examined. The results indicated that plant height, stem diameter, and fresh weight decreased as salt concentrations increased. Fresh weight declined from 18.4 g in control to 14.2 g in 1% NaCl, and plant height declined from 22.8 cm to 16.4 cm. However, salinity caused an increase in chlorophyll (SPAD), electrolyte leakage, and leaf relative water content. The application of biochar supported pepper growth under both salt-stressed and non-stressed conditions. Biochar levels of 2% and 4% improved plant growth by regulating chlorophyll, leaf temperature, RWC, and EL under control and moderate stress conditions. At the highest salinity level, increased biochar dose reduced the electrical conductivity (EC) of the growing medium under severe salinity conditions. In conclusion, applying 2% biochar promoted pepper plant growth under non-saline and moderate salinity stress, while a dosage of 6% should be effective in alleviating the EC value and the stress of severe salinity.