The synergistic effects of Ti and F co-doping on the structure and dehydrogenation properties of NaBH4 are investigated by using density functional theory calculations. The results show that Ti is more likely to substitute Na, while F tends to replace the H in the BH4 unit. It is found that Ti and F co-doped NaBH4 systems are more stable than Ti-doped NaBH4 system. The results of hydrogen desorption energies imply that the co-doped Ti and F decrease the strength of B H bonds. In addition, the hydrogen desorption energies decrease as increasing the concentration of F atoms. The dehydrogenation reaction of Ti and F co-doped NaBH4 is more likely to form TiB2, B, NaF, and H-2. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.