The main airports on at least three of the major islands -- Maui, Kauai and the Big Island of Hawaii -- were shut down as a precaution, and the U.S. Navy ordered all warships in Pearl Harbor to remain in port to support rescue missions as needed.
Authorities also ordered evacuations from low-lying areas on the U.S. island territory of Guam in the western Pacific, where residents there were urged to move at least 50 feet above sea level and 100 feet inland.
Guam initially appeared to have emerged unscathed.
"So far no waves," Lorilee Crisostomo told Reuters by telephone from Guam, roughly an hour after the tsunami was first due, though forecasters set a four-hour window in which a wave could hit the island.
Guam's homeland security agency advised tourists in high-rise hotels to take shelter on the sixth floor and above.
"A lot of people who aren't from Guam are panicking," said Homeland Security spokeswoman Alyssa Benito, adding, "We've never been hit by a major tsunami."
The U.S. Pacific Tsunami Warning Center said the warning extended from Mexico down the Pacific coast of South America.
The International Federation of Red Cross and Red Crescent Societies warned that the tsunami was currently higher than some Pacific islands in its path.
The quake off Japan's northeast coast was the biggest in 140 years and triggered tsunami waves of up to 10 meters (30 feet) that swept across farmland, carrying away homes, crops, vehicles and triggering fires.
On Easter Island, a Chilean territory in the South Pacific, authorities planned to move residents to higher ground hours before a possible tsunami was expected to reach the volcanic isle on Friday afternoon.
Chile's President Sebastian Pinera, whose country was hit by a devastating 8.8 magnitude quake and ensuing tsunamis that killed more than 500 people a year ago, called on Chileans to remain alert, but to continue with their daily routines.
GAS LINES, ALARMED TOURISTS
The tsunami warning issued late on Thursday for Hawaii prompted civil defense officials to order all Hawaiian coastal areas evacuated by 2 a.m. local time, about an hour before the first wave was expected to hit the islands at 1:00 p.m. GMT.
The evacuation zone included the famous Waikiki Beach, the main hotel and tourist hub in Honolulu on the island of Oahu.