The climber fell while at the 6,300-foot level of North Twin Sister, which is southwest of Mount Baker. A companion had to climb down to the 4,900-foot elevation to get a cellphone signal and call for help.
He reported that his partner appeared to have fallen 100 feet and had a severe head injury, but was alive at the time of his leaving for help.
Crews attempted a helicopter rescue Thursday afternoon, but the attempt was aborted due to inclement weather in the area, said Kent Catlin, deputy director of Whatcom County Emergency Management.
Ground crews eventually were able to get into the difficult and steep area where the fallen climber was located. By the time a crew reached the climber he had died of his injuries and he had to be left for the night until further efforts to recover him could be made.
On Friday morning, a helicopter team began the difficult task of trying to recover the man's body from the dangerous slope where he was found, Catlin said.
He said it appears that the climbers were not using any ropes or harnesses at the time of the accident and were free-climbing.
The climber's name is being withheld pending notification of his next of kin.