Attorneys Jeff Anderson and Marci Hamilton said Sandusky sexually abused the alleged victim "over one hundred times" and threatened to harm the victim and his family if he alerted anyone to the alleged abuse.
The former coach allegedly "molested multiple victims" dating back to the 1970s, according to the lawsuit.
Sandusky, meanwhile, has maintained his innocence throughout the scandal.
On Monday, his attorney said he is working with a private investigator in his quest to prove his innocence.
Attorney Joe Amendola said his client, who is free on $100,000 bail, is conducting his own investigation.
Sandusky, 67, is charged with 40 counts related to the alleged sexual abuse of eight young boys. He allegedly met the victims through The Second Mile.
Penn State, meanwhile, is expected hold a town hall forum Wednesday where students can ask questions about the child sex scandal that has shaken the campus.
University President Rodney Erickson and several campus students organizations will host the event Wednesday night.
"We all have questions," representatives of three campus groups wrote in a statement about the forum. " President Erickson is committed to making this healing process a community effort. As the University moves forward, there is a critical need for the student body and administration to have a dialogue about our plan for the future."
The longtime Nittany Lions defensive coordinator previously said in an interview with NBC's Bob Costas that he has been falsely accused, saying that he only "horsed around" with kids in showers after workouts. Amendola also has consistently said that Sandusky is innocent.
Penn State Athletic Director Tim Curley, 57, and the school's vice president for finance and business, Gary Schultz, 62, were each charged with one count of felony perjury and one count of failure to report abuse allegations about Sandusky. Their preliminary court hearing is set for December 16 at the Dauphin County Courthouse in Harrisburg, according to a news release from the county.
In addition, Penn State President Graham Spanier and iconic head football coach Joe Paterno lost their jobs soon after Sandusky's arrest, following criticism that the football program and university in general did not adequately handle the matter when allegations arose years earlier.
Several other people have also subsequently come forward, saying they too were sexually abused by Sandusky.