Soil salinity is a global problem, which is predicted to worsen in arid and semi-arid regions due to climate change. The aim of this study was to understand the remediation potential of biochar in alleviating salt stress by studying its effects on the growth and physiological parameters of the tomato (Solanum lycopersicum). A completely randomized design (CRD) was used where three different biochar doses (0%, 5% (v/v), and 10% (v/v)) were applied to the soil under saline (100 M) and non-saline conditions. Our results showed that while salt stress affected the plant growth negatively at all biochar doses, 5% and 10% biochar applications improved the overall plant performance under saline conditions. For the samples with salt stress, plant height and leaf area were increased by 43.1% and 45.3%, respectively, and physiological parameters, such as leaf relative water content and chlorophyll-a content, increased when 5% biochar was used. On the other hand, the highest increase rates in shoot fresh weight (113.7%), shoot dry weight (74.8%), the number of leaves (24.9%), root fresh weight (115.5%), root dry weight (62.5%) were obtained from 10% biochar amendment under saline conditions. Moreover, biochar amendment at both doses significantly decreased the superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activities, as well as malondialdehyde (MDA) and proline contents, which resulted in an improved plant growth due to the reduction of the oxidative and osmotic stresses. In conclusion, biochar amendment might be a promising approach to mitigate the adverse effects of salinity stress on tomato seedlings