WASHINGTON (AP) _ President Reagan and former President Nixon met for about an hour at the White House Thursday evening, presidential spokesman Marlin Fitzwater disclosed today.

Fitzwater said Nixon came to the White House at Reagan's invitation.

''I can't discuss the content of their conversations,'' he said.

He said First Lady Nancy Reagan and White House Chief of Staff Kenneth M. Duberstein also attended the meeting, held in the residential quarters of the White House.

Nixon was last at the White House for a meeting with the president early last year.

He also was at the White House in October 1981, along with former Presidents Carter and Ford, when Reagan asked them to meet with him before going to Egyptian President Anwar Sadat's funeral as his representatives.

John Taylor, Nixon's spokesman at his office in New York, said Nixon and Reagan also met at the Waldorf-Astoria Hotel in New York in September 1984, just before a speech by Reagan at the United Nations.

Taylor said Duberstein called Nixon about 10 days ago to say he would like to meet with him and to arrange a meeting. He said Nixon and Duberstein met Thursday morning and then joined the president and first lady for the late afternoon meeting.

Leslye Arsht, deputy White House secretary, confirmed that Duberstein met separately with the former president. She said the meeting was held outside the White House.

''It was a private meeting, and we will have no further comment,'' she said.

Taylor said he did not know what was discussed at the meetings.