With global climate change leading to an increase in the frequency of abnormally low temperatures, the yield of rice has significantly impacted. Due to extensive efforts over the past four decades, many genes involved in rice cold tolerance have been identified and cloned. Despite these endeavors, the molecular mechanisms of rice’s response to cold stress remain unclear. In this study, we used reverse genetics along with biochemical and molecular biology approaches to characterize OsRab6a, a small GTP-binding protein. Our findings revealed that OsRab6a positively regulates rice cold tolerance during both the bud and seedling stages. The expression of OsRab6a is induced by cold stress, particularly in seedling roots. Overexpression of OsRab6a enhances cold tolerance in transgenic rice, whereas the OsRab6a mutants exhibit the opposite phenotype. Furthermore, OsRab6a physically interacts with OsRAN2 under cold stress, functioning upstream of OsRAN2. These results suggest that OsRab6a plays an crucial role in regulating cold tolerance and the ABA signalling pathway. Our study elucidates the functional significance of OsRab6a in rice cold tolerance and provides potential strategies for enhancing the resilience of rice plants to cold stress.