Ceremonies took place in Pearl Harbor and at the National World War II memorial in Washington D.C..
Japan's surprise attack at Pearl Harbor killed 2,400 people and plunged the United States into World War Two.
Many of the servicemen who were killed were aboard the USS Arizona, Oklahoma and Utah.
Fewer than 200 survivors of the attacks there and on other military bases in Hawaii are alive.
Wednesday's commemoration in Hawaii took place at a pier overlooking the memorial to the sunken Arizona began and began with a moment of silence at precisely that time.
The bombing of Pearl Harbor took place at 7:55 a.m. Honolulu time on Dec. 7, 1941, famously dubbed "a date which will live in infamy" by U.S. President Franklin D. Roosevelt.
The battleship Arizona sank with 1,177 officers and crew on board and lies at the bottom of Pearl Harbor.
Wearing leis of fresh Hawaiian flowers around their necks, about 350 U.S. veterans of World War Two and their families received blessings and prayers for peace.
A performance by the Navy's Pacific Fleet Band was made bittersweet by the knowledge that every member of the USS Arizona band, one of the Navy's best, died that day.
Two families were to participate in a private ceremony in which the ashes of crew members who survived the attack and died later were to be interred in a turret of the Arizona.
Across the United States on Wednesday, Americans remembered those who died at Pearl Harbor and the long, difficult war that followed.
Veterans also gathered at the National World War II memorial in Washington D.C..
U.S. Vice-President elect Mike Pence and Arizona Senator John McCain attended the ceremony.
"Many American families were changed that day. Many endured the pain of separation from loved ones, and many suffered the pain that time never completely heals, the loss of children, and parents and siblings. America too was changed forever. For the events of that infamous day, for the events that infamous day, the day that summoned the might and courage and compassion of the American people to a World War,' said McCain, a Vietnam veteran.
The attack on Pearl Harbor was launched to destroy the U.S. Pacific fleet and with the aim of keeping the United States out of the war.
It did not have the intended effect. The United States declared war on Japan on December 8th, 194 and three days later, Germany declared war on the United States.