The 28-year-old man who died was not immediately identified.
Four of the crash victims were examined by medics and released, while five other soldiers sustained minor injuries. Reports show one soldier was seriously injured.
The military shuttle was transporting re-deployed 7th Infantry soldiers from SeaTac back to JBLM. Military officials say some of the soldiers were returning from Afghanistan.
"That's one of the things that kind of hits all of us right in the heart when you think about it this. I mean, those individuals serve our country and they work hard for us," Trooper Guy Gill said. "That pulls at all of our heart strings, because we know how hard they work for us, and to lose a life like this just doesn't seem right."
The shuttle was in the southbound HOV lane when it struck the median and knocked over a light pole into northbound traffic, fire officials said.
The light pole was difficult to remove because it was still attached to the barrier and caused traffic delays well into Thursday night.
Northbound I-5 backups reached about 7 miles from Nisqually to Thorne Lane, according to Washington DOT.
The cause of the crash is under investigation. Troopers say there's no indication the driver was impaired.