Salt, cold, and drought stress are the adverse environmental conditions in marine Antarctic that limited plant growth and distribution. Plant leucine-rich repeat receptor-like kinases (LRR-RLKs) play crucial roles in sensing external signals to regulate gene expression. However, only limited information is available on LRR-RLK functions in bryophytes. Here, a putative LRR-RLK gene, PnLRR-RLK2, was cloned and characterized from the Antarctic moss Pohlia nutans. Phylogenetic analysis showed that PnLRR-RLK2 belongs to the Arabidopsis thaliana LRR II subgroup and its expression was significantly induced by abiotic stresses. Subcellular localization analysis revealed that it was a plasma membrane protein. PnLRR-RLK2 heterologous expression in Arabidopsis increased the salinity, drought, H2O2, and abscisic acid (ABA) tolerance than that in wild-type plants. Furthermore, PnLRR-RLK2 overexpression increased the expression of salt stress/ABA-responsive genes in transgenic Arabidopsis germination seedlings. Taken together, these results suggested that PnLRR-RLK2 as a positive regulator conferred salt and drought stress response associated with the regulation of the antioxidative system and the ABA-mediated signaling network.