At least one attack occurred in Philadelphia, the suit says. According to his lawyer, the boy tried to resist and later considered reporting Sandusky to authorities, but the legendary coach threatened him.
"He said: Nobody will believe you, and if you do, something will happen to your family," lawyer Jeff Anderson said at a news conference.
The 26-page filing does not name the accuser and Anderson refused to describe or identify him except as "John Doe A." He said the man, who now lives outside Pennsylvania, reported the allegations to law enforcement authorities on Tuesday, a day before he filed the suit.
Sandusky's lawyer, Joseph Amendola, did not respond to requests for comment. He and Sandusky have said the coach is innocent of the criminal charges against him.
Officials at Penn State and the Second Mile said they could not comment on the lawsuit because they had not yet reviewed it.
If true, the claims would add a new dimension to the Sandusky case - suggesting a sustained period of abuse that began earlier, in 1992, and lasted longer, four years, than any other claims thus far.
Prosecutors have charged Sandusky with abusing at least eight boys between the mid-1990s and 2008.
Nils Frederiksen, a spokesman for state Attorney General Linda Kelly, said the office could not confirm if Anderson or his client had been in contact with investigators.
In a statement released by his lawyer, John Doe A said he came forward after the recent reports about Sandusky.
"I never told anybody what he did to me over 100 times at all kinds of places until the newspapers reported that he had abused other kids," the statement said. "The people at Penn State and Second Mile didn't do the things they should have to protect me and the other kids."
Based in St. Paul, Minn., Anderson has represented hundreds of sexual abuse victims worldwide. He and his cocounsel on the case, Marci Hamilton, filed a half-dozen claims this year against the Archdiocese of Philadelphia and its priests and officials.
John Doe A's suit says he met Sandusky in 1992 through the Second Mile, the charity for at-risk youth Sandusky founded in 1977. The abuse began almost immediately, the lawyers said.
Similar to allegations spelled out in the grand jury presentment against Sandusky, John Doe A claims the coach showered him with gifts, took him to a bowl game and on trips with the football team, and often invited him to sleep at his home in State College.
The lawsuit claims that if university or charity officials had investigated Sandusky, they would have found the coach "had been molesting children since at least the 1970s."
Anderson acknowledged he had no proof of that claim, but rather "indications" based on the evidence cited in the grand jury report and long-term studies of pedophile behavior.
"We're at the tip of the iceberg here," he said.
The filing came one day after two Philadelphia-area lawyers said they had been hired by a Clinton County teenager whose accusations launched the wider investigation into Sandusky two years ago.
Lawyers Michael J. Boni and Slade H. McLaughlin announced they represent the Lock Haven youth - known in the grand jury report as Victim 1 - and his mother.
Two other attorneys, Benjamin Andreozzi of Harrisburg and Andrew Shubin of State College indicated they also represent victims of abuse by Sandusky. Others are expected to follow.
Sandusky faces a preliminary hearing in Centre County on Dec. 13, when prosecutors could disclose if they have identified more potential victims and how many.
Three days later is a scheduled hearing for two current or former university officials charged with covering up one attack. The grand jury report said athletic director Tim Curley and former vice president Gary Schultz failed to tell authorities in 2002 that a graduate assistant claimed to see Sandusky raping a 10-year-old boy in the football locker room showers.
Both Curley and Schultz maintain they were not told a sexual assault had occurred - a claim backed by the university's former president Graham B. Spanier and head football coach Joe Paterno.
Penn State's board of trustees fired Spanier and Paterno in the wake of the allegations and placed Curley on administrative leave pending the resolution of his criminal case. Schultz has returned to retirement.
Contact staff writer Jeremy Roebuck at 267-564-5218, firstname.lastname@example.org, or @inqmontco on Twitter. Read his blog, "MontCo Memo," at www.philly.com/montcomemo