The woman has told investigators she remembers little of the alleged assault, which she said occurred after she became intoxicated at an off-campus party in Annapolis, her attorney said.
Susan Burke, the Washington-based attorney, said the woman learned from friends and social media that three football players were claiming after the party that they had had sex with her while she was incapacitated.
The allegations out of the nation's premier training ground for Navy and Marine Corps officers come as the military grapples with rising reports of sexual assaults within the ranks. President Barack Obama, during his commencement address at the academy last week, said the assaults undermine the military's strength and must be stopped.
Burke said the Navy investigated the allegations last year, but only her client was disciplined, for underage drinking. Burke said the woman's alleged attackers "suffered no adverse consequences," and were permitted to continue playing football.
Army Col. Steve Warren, the Pentagon spokesman, said the investigation into the April 2012 incident is continuing. He referred further questions to the Naval Academy.
Cmdr. John Schofield, an academy spokesman, confirmed an investigation was underway but declined to provide details.
Schofield said academy leaders were "monitoring the progress of this investigation and evaluating the appropriate options for adjudication."
He added: "It is an ongoing matter and any other public comment on this potentially compromises the military justice process."
The football players have not been named.
The academy declined to make Vice Adm. Michael Miller, the academy's superintendent, or football coach Ken Niumatalolo available to comment.
News of the investigation comes amid growing scrutiny of commanders' efforts to confront the long-standing problem of sexual assaults in the military. Based on surveys, the Pentagon estimated this month that as many as 26,000 service members were sexually assaulted last year, up from 19,000 the year before.
The number of incidents reported rose to 3,374, up 6 percent from the year before.
That Pentagon report came days after the officer in charge of the Air Force sexual assault prevention and response program was charged with groping a woman in a Northern Virginia parking lot.
More than 30 instructors at Lackland Air Force Base, Texas, have been investigated in a continuing probe of sexual misconduct involving more than 60 trainees; at least nine instructors have been convicted and sentenced to prison or hard labor.
Defense Secretary Chuck Hagel has pledged more action on sexual assaults.
Obama told the academy's Class of 2013 that "those who commit sexual assault are not only committing a crime, they threaten the trust and discipline that make our military strong."
"That's why we have to be determined to stop these crimes, because they've got no place in the greatest military on Earth," he said.
The recently accused include a former academy instructor now facing a court-martial.
Marine Corps Maj. Mark A. Thompson, who taught history at the academy, has been accused of assaulting a female midshipman in his Annapolis apartment after the annual croquet match between the academy and St. John's College in 2011.