Salinity is a major constraint to crop productivity and mechanisms of plant responses to salinity stress are extremely complex. “Hordeum marinum” is a salt tolerant barley species, which could be a good source to evaluate salt-tolerance patterns. Proteomics is a powerful technique to identify proteins involved in plant adaptation to stresses. We applied a proteomic approach to better understanding the mechanism of plant responses to salinity in a salt-tolerant genotype of barley. At the 4-leaf stage, plants were exposed to 0 (control treatment) or 300 mM NaCl (salt treatment). Salt treatment was maintained for 3 weeks. Total proteins of leaf 4 were extracted and separated by two-dimensional gel electrophoresis. More than 290 protein spots were reproducibly detected. Of these, 20 spots showed significant changes to salt treatment compared to the control: 19 spots were upregulated and 1 spot was absent. Using MALDI-TOF/TOF MS, we identified 20 cellular proteins which represented 11 different proteins and were classified into five categories. These proteins were involved in various cellular functions. Upregulation of proteins which involved in protein processing (ribosomal protein, cullin family, cp31AHv protein and RNA recognition motif (RRM) superfamily), photosynthesis (Ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) and Ribulose bisphosphate carboxylase/oxygenase activase (rubisco activase)), energy metabolism (cytosolic malate dehydrogenase (cyMDH) and fructokinase), oxygen species scavenging and defense (cystatin and thioredoxin) may increase plant adaptation to salt stress.