Calcium borohydride (Ca(BH 4 ) 2 ) has attracted significant interest in recent years due to its strong potential for hydrogen storage applications. Here, we report the pressure-induced structural transformations of Ca(BH 4 ) 2 probed by combined Raman spectroscopy and infrared (IR) spectroscopy up to 10.4 GPa at room temperature. Starting with the R phase in an orthorhombic structure, Ca(BH 4 ) 2 was found to undergo several transformations upon compression, as evidenced by the sequential changes of characteristic Raman and IR modes as well as by examining the pressure dependences of these modes. In situ Raman and IR measurements collectively provided consistent information about the structural evolutions of Ca(BH 4 ) 2 under compression. Decompression measurements on Ca(BH 4 ) 2 suggest that the pressure-induced transformations are reversible in the entire pressure region. The combined Raman and IR data allowed for an in-depth analysis of possible high-pressure structures of Ca(BH 4 ) 2 .