An air-stable LiBH4 polymeric composite was successfully prepared by modifying LiBH4 with a gas-barrier polymer matrix, poly(methylmethacrylate) (PMMA). The as-prepared LiBH4@PMMA composite started to dehydrogenate at 53 °C with the first main dehydrogenation peak at 116 °C, and 5.2 wt% of hydrogen released at 162 °C within 1 h.