Roger Stillwell told a federal magistrate that he had been given hundreds of dollars worth of football and concert tickets from Abramoff, who at the time was lobbying for the Commonwealth of the Northern Mariana Islands.
Stillwell was with the Interior Department's insular affairs office, which handles issues involving the island government.
Documents filed as part of Stillwell's plea do not indicate whether he is providing authorities with evidence against others who might be involved in the case.
Stillwell received four tickets to a Washington Redskins game in December 2003 valued at $316 with an actual cost of $2,147, prosecutors said. He also accepted two tickets to a 2003 Simon and Garfunkel concert worth $166, prosecutors said.
Neither prosecutors nor defense attorneys would say whether Stillwell provided Abramoff anything in return for the gifts.
"He recognizes that his decision on how to treat gifts from Mr. Abramoff was inexcusable. For that he has deep remorse," defense attorney Justin P. Murphy said in a prepared statement. Murphy said Stillwell had been friends with Abramoff and his family for many years before he took the Interior job.
U.S. Magistrate Judge Alan Kay set sentencing for Oct. 26. Stillwell faces up to a year in prison.
So far, the Abramoff probe has resulted in guilty pleas by two ex-aides to former House Majority Leader Tom DeLay, R-Texas, a former chief of staff to Rep. Bob Ney, R-Ohio, and Abramoff himself. A former White House official was convicted on unrelated charges.
Ney announced this week that he would abandon his re-election campaign, acting under pressure from party officials who feared he would lose to a Democratic challenger. He has not been charged and has denied any wrongdoing.