Pot experiments over two successive seasons 2019-20 to 2020-21 were conducted to study the effect of biochar application on the growth and some physiological parameters of pot marigold grown under salt stress. A factorial experiment block design was performed with 2 levels of biochar (5%, 10%) and 3 levels of saline water (1000, 2000 and 3000 mgl^-1 of NaCl) in addition to control. Results showed that, application of biochar at both levels mitigated the negative effect of salt stress by enhancing the biomass duration, membrane stability index and relative water content of plants. At high level of salinity, biomass duration was increased by 55 and 31% as well as membrane stability index by 22 and 28% in both seasons, respectively after application of biochar 10%. Also, relative water content was increased by 15% after application of 5% of biochar at first season. Beneficial effect of biochar may be correlated with reduction of salinity in soil solution by 37.9% after application of biochar at 10%, as well as decrease of Ca²⁺, Na⁺ and K⁺ concentrations. It can conclude that application of 10% biochar was recommended for pot marigold, which irrigated with saline water.