Selenium (Se) has a versatile chemistry. Therefore, it is present in a wide variety of materials on Earth. Although it is not an essential element for plants, Se provides several survival and ecological advantages. Puccinellia distans (P.distans) is weeping alkali grass which has a relatively fast growth rate and produces a large biomass. It can also hyperaccumulate extreme concentrations of boron and tolerate high levels of salinity. It is known that some plant species can tolerate high concentrations of soil salts and boron while hyperaccumulating Se in their leaves. Therefore, in this study, the Se accumulation and tolerance capacity of P. distans were investigated, and the plant’s Se tolerance mechanism was elucidated using a transcriptomic approach. The results of this study indicated that P. distans accumulated more than 100 mg Se kg-1 in its shoots. Therefore, P. distans was discovered to be a novel Se accumulator plant. Biochemical analyses and RNA sequencing results helped us to decipher the Se tolerance and accumulation mechanism of P. distans. Accordingly, the tolerance mechanism was found to be associated with the upregulation of genes involved in sulfate, selenocompound and antioxidant pathways. Here, we suggest that upregulation of Se assimilation and stress responses genes may have been due to induction of jasmonic acid signaling. In addition, we propose that the cell wall may play an important role in restriction of Se movement to the cytoplasm. Also, we put forward that sequestration of selenate inside the vacuole may be a way that Se accumulates in cells.