The victims were among a group of six people climbing Sunday afternoon on Sharkfin Tower, about 20 miles east of Marblemount, park spokesman Tim Manns said.
A fourth member of the group was seriously injured but the other two were not hurt. All six are from Washington state, Manns said.
Early information indicated that the accident involved a fall, Manns said. Approaching the Sharkfin Tower peak requires crossing a glacier and then scaling a rock face.
Other climbers in the area reported the accident by cell phone. Rescuers set out on foot late Sunday and hoped to reach the group Monday morning. Rain during the night hampered other rescue efforts but rangers hoped to send a helicopter to the site Monday, Manns said.
Sharkfin Tower is 8,120 feet high and located along a ridge of peaks in the Boston Basin area, 90 miles northeast of Seattle.