The former Liberia national captain will now succeed his great rival and incumbent, Ellen Johnson Sirleaf as the 25th president of Liberia.
Weah retired from professional football in 2003 and soon became involved in politics when he formed the Congress of Democratic Change in 2005.
As Liberia's most famous son, Weah attracts huge crowds and has a faithful youth following in a country where a fifth of the electorate is aged between 18 and 22.
Weah led the first round of voting on October 10 but didn't get enough votes to win outright.
This is the second time he has run for the presidency in Liberia, the first being in 2005.
Weah topped the first round of voting with 38.4 percent while Boakai came second with 28.8 percent. The failure of any candidate to secure an outright majority forced the run-off.More news: Libya Pipeline Blast Sends Oil Prices Soaring
Former soccer star George Weah has defeated Vice President Joseph Boakai to win Liberia's presidential run-off election with 61.5% of the vote based on 98.1% of ballots cast, the election commission said.
He is now senator for Montserrado County in Liberia after being elected in 2014.
But Mr Weah's election is not without controversy, as his running mate is Jewel Taylor, former wife of the warlord and ex-President Charles Taylor, who is serving a jail sentence in the United Kingdom for war crimes.
Liberia, founded by freed United States slaves in the 19th Century, has not had a smooth transfer of power from one elected president to another since 1944.