Drought and salinity are major factors limiting crop productivity worldwide. DREB (dehydration-responsive element-binding) transcription factors play important roles in plant stress response and have been identified in a wide variety of plants. Studies on DREB are focused on the A-1 (DREB1) and A-2 (DREB2) groups. Studies on A-5 group DREBs, which represent a large proportion of the DREB subfamily, is limited. In this study, we characterized and analyzed the stress tolerance function of ScDREB10, an A-5c type DREB gene from the desert moss Syntrichia caninervis. Transactivation assay in yeast showed that ScDREB10 had transactivation activity. Transient expression assay revealed that ScDREB10 was distributed both in the nucleus and cytosol of tobacco leaf epidermal cells. Overexpression of ScDREB10 significantly increased the germination percentage of Arabidopsis seeds under osmotic and salt stresses, and improved the osmotic and salt stress tolerances of Arabidopsis at the seedling stage and is associated with the expression of downstream stress-related genes and improved reactive oxygen species (ROS) scavenging ability. Our study provides insight into the molecular mechanism of stress tolerance of A-5 type DREB proteins, as well as providing a promising candidate gene for crop salt and drought stress breeding.