The Conservative received 50.24% of the vote in an easy win for the party.
Speaking to the BBC after his win, he said: "I'm very excited by some of the results.
"Overall, it has been an amazing night for the Conservatives considering what the polls were saying only a few hours ago - it's a remarkable turnaround."
He said he'd serve out his remaining year as Mayor, adding: "I intend to serve the people of Uxbridge & South Ruislip to the best of my abilities."
The final count was announced at Brunel University, in Uxbridge, at around 4.30am on Friday (May 8), ending hours of tense anticipation.
Mr Johnson had been hotly tipped to win the seat, which had been held by fellow Tory Sir John Randall since its creation in 2010.
Mr Johnson received 22,511 votes, beating his closest contender, Labour's Chris Summers, by 10,695.
Voter turnout for the constituency was 63.60% - up from 60.99% in 2010.
Mr Summers received 11,816 votes; Liberal Democrat Mike Cox received 2,215; UKIP's Jack Duffin got 6,346; the Green Party's Graham Lee got 1,414; The Trade Unionist and Socialist Coalition's Gary Harbord won 180; the Eccentric Party's Lord Toby Jug won 50; the Official Monster Raving Loony Party's Alan 'Howling Laud' Hope won 72; the Realists' Party's Jane Lawrence got 18; the Communities United Party's Sabrina Moosun got 52; and independents Michael Doherty, James Jackson and Jenny Thompson got 39, 14 and 84 respectively.
The number of spoiled ballots was 206.
Mr Johnson, who was MP for Henley from 2001 to 2008, has previously said that if elected into the House of Commons he would only vote for HS2 if certain conditions were met.
He is also against building a third runway at Heathrow Airport, but has admitted he still holds hopes of resurrecting his plans for a 'Boris Island' airport hub on the Thames Estuary, which some fear would mean closing Heathrow altogether.
Some, including his rival election candidates, have previously expressed concerns Mr Johnson will not be able to adequately fulfil his role as an MP while remaining London mayor.