Banana is one of the plants with low salt tolerance and raising its ability to withstand salt stress contributes to increasing its production. Silicon (Si) is one of the important elements in increasing the salt stress resistance in plants. Therefore, Si-rich biochar has been suggested to improve the salt resistance of Williams (WL) and Grand Nain (GN) banana cultivars. Water salinity (tap water, 2, 4, and 6 dS m⁻¹) and Si-rich biochar with low (LSiB) or high rate (HSiB) in a pot experiment were studied. Si-rich biochar significantly mitigated the salt stress and improved the growth of WL and GN banana cultivars. Si-rich biochar was effective in enhancing chlorophyll, carotenoids, calcium (Ca⁺⁺) and potassium (K⁺) in banana leaves. HSiB was more effective than LSiB in mitigating the accumulation of sodium (Na⁺) in the plant leaves. HSiB raised the phenolic, carbohydrate, and proline in WL leaf tissues by 35, 49, and 14%, while these increases were 20%, 44%, and 21% in the case of GN cultivar. Banana leaves exposed to salt stress had higher levels of malondialdehyde (MDA), while Si-rich biochar reduced those levels. Antioxidant enzymes activity were raised by salt stress, and HSiB performed better than LSiB at boosting antioxidant enzyme activity. The production of osmo-protectants such as phenols, carbohydras, and proline were higher in the banana plants treated with HSiB compared to LSiB ones. Si-rich biochar mitigated the salt stress by increasing the uptake of Ca and K, improving the antioxidant defense, and enhancing the production of combatable solutes.