The downing killed all 243 passengers and 16 crew members, and 11 people on the ground in Lockerbie, Scotland.
"I am proud to reaffirm our ongoing commitment to ensuring justice for the 270 innocent victims whose lives were violently cut short, exactly 23 years ago, and for the family members and friends whose lives were forever changed on that tragic day," Holder said in prepared remarks.
Holder called the bombing "a shameful and senseless act of cowardice" that "shocked the world, and had a dramatic and far-reaching impact on international affairs -- creating a new global community of mourners, supporters and advocates."
He added: "Here today, on this nation's most hallowed ground, we remember and pay tribute to each of [the victims]. And, this year, we also honor the contributions of those who have sought justice on their behalf ... ."
U.S. officials accused Libyan intelligence of carrying out the bombing. The only person convicted in the bombing, Abdelbaset Ali Mohmed al-Megrahi, was released from a Scottish prison on compassionate grounds in 2009 after more than eight years in prison.
Supposedly dying of cancer, he has been living in Libya.
Notable deaths of 2014 [PHOTOS]
Cyclist struck and dragged underneath car