<p>Nowadays, salt stress considered an important environmental challenge for the agriculture which is aggravated by global warming, thereby, markedly decreasing the biomass production and crop yield worldwide. Nanoparticles are widely applied to strengthen plants against environmental stresses. Carbon based nano-chemicals and especially carbon dots (CDs) are regarded as highly beneficial nanoparticles for applications in agriculture thanks to their properties. CDs generated from urea and citric acid in this research demonstrated great physico-chemical characteristics consisting of biocompatibility, strong fluorescence, solubility in water and functional groups on their surface. In this study, CDs were employed to improve the salt tolerance of tomato as a physiological model plant. Salt stress reduced the fresh biomass and total height of tomato seedlings. Further, proline and the total content of carbohydrates increased to adjust the osmotic potential of cytoplasm facing high NaCl levels. Salinity heavily declined seed germination indices as well. Contrary to salt-treated seedlings, incubation with CDs had positive effects on preliminary physiological parameters i.e. growth and total length in salt-stressed and non-stressed plants. Likewise, some osmotic balancing markers including proline and carbohydrates considerably increased in combined CDs- and NaCl-treated plants relative to salt-exposed ones. Further, the ameliorating influence of CDs on seed germination percentage and rate was noticed in salinity exposed seeds. Thus, CDs are appropriate candidates providing an efficient approach in developing modern and acclimatized agriculture and increasing crop yield.</p>