Steve Garban said in a letter his presence on the board had become "a distraction and an impediment" to its efforts to move forward.
Garban, who had stepped down as board chairman after Sandusky's November arrest but had remained a board member, was harshly criticized over his handling of the crisis that engulfed Penn State, and he faced persistent calls from alumni and fellow board members to resign.
An internal investigation by former FBI Director Louis Freeh found that Garban was briefed twice about developments in the Sandusky case but didn't share what he knew with the entire board, depriving trustees of a chance to prepare for the worst crisis in Penn State's 157-year history.
Freeh's 267-page report portrayed a disengaged board that handed too much responsibility to the university president and failed to investigate deeply enough once it became aware of a grand jury probe.
After the report's release, trustees accepted responsibility for a failure of oversight and said they were "deeply ashamed." Board Chairwoman Karen Peetz, who announced Garban's resignation in a letter on the board's website, said at the time that no trustee would step down, however.
Garban didn't immediately return a call seeking comment Thursday night. In his resignation letter to Peetz, he said he had "devoted" his adult life to Penn State.
"It has been a privilege and an honour to serve the university that has done so much for me," the letter stated. "Indeed, it is precisely because of my deep gratitude to and respect for my beloved alma mater that I now step aside."
He called the past months "some of the most painful of my life."
"The horrific allegations that came to light in November have haunted us all, but nothing we have experienced compares to that of Jerry Sandusky's victims," he said. "My thoughts and prayers will remain with them always."
In a response posted on the trustees' website, Peetz thanked Garban for his years of service to Penn State.
While Garban is the first trustee to resign in the wake of the Sandusky scandal, he's not the first board casualty. Incumbent trustee Anne Riley lost re-election last spring as alumni upset over the board's handling of the crisis picked three new trustees — all of whom campaigned on a reform platform — to sit on the 32-member panel.
A 1959 Penn State graduate, Garban worked at the university for 33 years, the last 12 as treasurer and senior vice-president of finance and operations. Alumni first elected him to the board of trustees in 1998, and he began his fifth three-year term in 2010.
Some trustees felt he was too close to ousted university president Graham Spanier, according to the Freeh report.
"Some trustees thought Garban's history of being previously employed at Penn State, where as (senior vice-president) he reported directly to Spanier, hampered his ability to lead the board," the report said.
In April 2011, the report said, Spanier told Garban about a grand jury investigation of Sandusky. Garban, in turn, failed to alert fellow board members. Garban told investigators that Spanier downplayed the Sandusky probe, and he recalled his former boss saying, "It was the third or fourth grand jury and nothing would come of it," the report said.
Then, on Oct. 28, Garban learned from Penn State's chief lawyer that two university administrators were about to be charged with failing to report suspected child abuse. Garban told investigators he was "astounded" when he saw Sandusky in the Nittany Lion Club at Penn State's home game against Illinois on Oct. 29. Yet he informed only two other trustees — James Broadhurst and John Surma — that charges against Sandusky, Athletic Director Tim Curley and Vice-President Gary Schultz were imminent.
Former general counsel Cynthia Baldwin told Freeh's investigators that she thought Garban, as "conduit to the board," would have alerted his colleagues about the Sandusky investigation. Garban told trustees he kept it from them because he was not sure that criminal charges would come to pass, according to the Freeh report.
Garban stepped down as board chairman three days after Sandusky's Nov. 5 arrest, handing the job to Surma, the vice chairman. One day later, the board ousted revered football coach Joe Paterno and Spanier.
Sandusky later was convicted of abusing 10 boys, some on campus. He has maintained his innocence while awaiting sentencing.
Schultz and Curley await trial on charges of perjury and failure to report suspected child abuse. They deny the allegations against them. Spanier is not charged, and his attorneys have criticized the Freeh report, saying it contains inaccuracies.