Bill Lincoln, a former state Senate Democratic floor leader, said in a Friday statement that he's no longer able to do the job because of "personal stress" and ongoing health issues.
He didn't specifically mention last week's grand jury report that alleged a "pay-to-play" culture at the turnpike commission.
He had served as a turnpike commissioner for eight years after being nominated by former Gov. Ed Rendell.
Lincoln testified before the grand jury under a grant of immunity. The grand jury says he admitted that he received gift certificates and failed to report them on his annual statement of financial interests.