Salinity is considered a top challenge facing food security, globally. The effects of different amounts of date palm-derived biochar on spinach (Spinacia oleracea cv. Balady) affected by saline water irrigation were studied in a pot experiment carried out at the months of October and November during the winter season of 2021. Results showed that salt stress negatively affected the morphological and physiological parameters of spinach plants such as the shoot system (4%, 13.3% at salinities of 5 and 10 dSm-1, respectively). The addition of biochar significantly increased the root length under all salt stress conditions. The results showed that the addition of biochar resulted in improved biomass weight at 2.5 and 5 dSm-1 salinity at all levels. The number of leaves increased by only 3.08% at 2.5 dSm-1 salinity, while it decreased by 13.8 and 35.2% at the next two salinities; 5.00 and 10.0 dSm-1, respectively. The overall reduction values were achieved corresponding to the higher saltwater concentration (10 dSm-1) compared to the control plants. It seems that the addition of biochar up to 1% also showed promising results in all observations. The results obtained from measuring membrane stability index (MSI) and electrolyte leakage (EL) showed that all stressed plants had increased MSI values and decreased EL values compared to the control. Sodium, soluble sugars, and proline levels significantly increased corresponding to saline water. Soil amendments utilizing biochar resulted in a significant improvement in plant growth and alleviated salt stress.