Adama Barrow, who reportedly worked at Argos in Holloway Road, defeated longtime president Yahya Jammeh in a surprise result.
Mr Jammeh, who came to power following a coup in 1994, is expected to concede defeat following 22 years of leadership.
Gambia’s electoral commission chairman Alieu Momarr Njai said Mr Barrow received 263,515 votes, Mr Jammeh won 212,099 and a third candidate, Mama Kandeh, received 102,969.
He returned to Gambia in 2006 to set up his own business and received the presidential nomination to lead a coalition of seven parties in this year’s election.
During his campaign, he promised to revive the Gambian economy which has forced thousands of people to travel to Europe in search of jobs.
Mr Barrow said on voting day that he strongly believed Gambians were ready for change, adding: “He is not going to be re-elected – his era is finished.”