Soil health is essential and irreplaceable for plant growth and global food production, which has been threatened by climate change and soil degradation. Degraded coastal soils are urgently required to reclaim using new sustainable technologies. Interest in applying biochar to improve soil health and promote crop yield has rapidly increased because of its multiple benefits. However, effects of biochar addition on the saline–sodic coastal soil health and halophyte growth were poorly understood. Response of two halophytes, Sesbania (Sesbania cannabina) and Seashore mallow (Kosteletzkya virginica), to the individual or co‐application of biochar and inorganic fertilizer into a coastal soil was investigated using a 52 d pot experiment. The biochar alone or co‐application stimulated the plant growth (germination, root development, and biomass), primarily attributed to the enhanced nutrient availability from the biochar‐improved soil health. Additionally, the promoted microbial activities and bacterial community shift towards the beneficial taxa (e.g. Pseudomonas and Bacillus) in the rhizosphere also contributed to the enhanced plant growth and biomass. Our findings showed the promising significance because biochar added at an optimal level (≤5%) could be a feasible option to reclaim the degraded coastal soil, enhance plant growth and production, and increase soil health and food security. Biochar alone or co‐applied with fertilizer enhanced the growth (e.g. germination, root development, and biomass) of two local halophyte plants, primarily attributed to the enhanced nutrients availability (i.e. NAE and PAE), the elevated microbial activities in rhizhosphere and bacterial community shift towards the bacterial taxa responsible for C‐stabilizing in soil, phosphate solubilizing and N‐fixing. The co‐application of biochar and fertilizer (≤5%) had greater benefits for the halophyte growth than the biochar or fertilizer alone. The biochar‐enhanced plant growth and biomass in coastal wetlands could potentially buffer the negative effect of climate change, thus enhance soil health and food security. This is the first report on examining the rhizosphere microbial response (i.e. the shifts in bacterial community composition) to the biochar‐enhanced nutrient bioavailability for halophyte growth.