Desmonostoc salinum CCM‐UFV059 (Desmonostoc) is a novel cyanobacterial strain of the order Nostocales isolated from a saline‐alkaline lake. The acclimation towards salt and desiccation stress of Desmonostoc was compared to the related and well‐characterized model strain Nostoc sp. PCC7120 (Nostoc). Salt–stressed cells of Desmonostoc maintained low cellular Na⁺ concentrations and accumulated high amounts of compatible solutes, mainly sucrose and to a lower extent trehalose. These features permitted Desmonostoc to grow and maintain photosynthesis at 2‐fold higher salinities than Nostoc. Moreover, Desmonostoc also induced sucrose over‐accumulation under desiccation, which allowed this strain to recover from this stress in contrast to Nostoc. Additional mechanisms such as the presence of highly unsaturated lipids in the membrane and an efficient ion transport system could also explain, at least partially, how Desmonostoc is able to acclimate to high salinities and to resist longer desiccation periods. Collectively, our results provide first insights into the physiological and metabolic adaptations explaining the remarkable high salt and desiccation tolerance, which qualify Desmonostoc as an attractive model for further analysis of stress acclimation among heterocystous N₂–fixing cyanobacteria.