Liberia’s president, George Weah, conceded defeat on Friday night in his bid for a second term, after a tight runoff against Joseph Boakai, a 78-year-old political veteran, in an election that was considered a test of democracy in the West African nation.

Mr. Boakai, who had served as vice president for 12 years under the former president, Ellen Johnson Sirleaf, defeated Mr. Weah, a 57-year-old former soccer star, by a razor-thin margin.

The country’s national election commission stopped short of declaring a winner on Friday afternoon, but announced that with more than 99 percent of the ballots counted, Mr. Boakai held 50.89 percent of the votes, and Mr. Weah 49.11 percent. It was the nation’s tightest election in two decades.

Mr. Weah said in a radio address broadcast late on Friday evening that while his party had lost the election, “Liberia has won.”

“This is a time for graciousness in defeat, a time to place our country above party, and patriotism above personal interest,” he said.

It’s the first time since the early 1900s that an incumbent president of Liberia has not been re-elected after serving one term. The swearing-in ceremony is scheduled for January.