SummaryGlycine‐rich RNA‐binding proteins (GR‐RBPs) have been implicated to play roles in post‐transcriptional regulation of gene expression in plants under various stress conditions, but the functional roles of GR‐RBPs under stress conditions remain to be verified. Here, we examine the biological roles of a GR‐RBP, designated atRZ‐1a, in Arabidopsis thaliana under stress conditions. atRZ‐1a was expressed ubiquitously in various Arabidopsis organs including stems, roots, leaves, flowers, and siliques. The transcript level of atRZ‐1a increased markedly by cold stress, whereas its expression was marginally downregulated by drought stress or abscisic acid treatment. Germination and seedling growth of the loss‐of‐function mutants were retarded remarkably compared with those of the wild type under cold stress. In contrast, the transgenic Arabidopsis plants that overexpress atRZ‐1a displayed earlier germination and better seedling growth than the wild type under cold stress. Moreover, the atRZ‐1a‐overexpressing transgenic Arabidopsis plants were more freezing tolerant than the wild‐type plants. Heterologous expression of atRZ‐1a in Escherichia coli demonstrated that the E. coli cells expressing atRZ‐1a displayed much higher growth rate than the non‐transformed cells after cold shock. These results provide evidence that atRZ‐1a affects seed germination and seedling growth under low temperature and plays a role in the enhancement of freezing tolerance in Arabidopsis plants.