The anti-European Union figurehead stands to win USD 2,500, plus his original stake back, after placing the bet at odds of 5/2, or USD 5 won for every USD 2 bet.
The former trader placed the bet with bookmakers Ladbrokes in a branch in the City of London financial district.
"Just been down the bookies. We're gonna win this!" Farage said on Twitter.
"The odds are moving in our favour and I'm very confident I'll be back after the referendum to collect my winnings."
"Remain" is on 51 per cent and "Leave" on 49 per cent according to the WhatUKThinks website's average of the last six polls, with the Leave camp gaining ground.
But the bookmakers' odds suggest the in camp is well ahead, at 5/2 for Leave and 3/10 for Remain -- a 10 in 13 chance of happening.
Ladbrokes said plenty of large bets had been staked in its City of London branches on Britain remaining in the EU -- but this was the biggest placed on leaving.
"While the odds are still stacked against him, he was confident he'll be returning to pick up some cash to pay for the independence beers in a few weeks.
