Betfair, the world's largest bettingwebsite, said it had sold 16.2m shares in the offering, excluding an overallotment option, or 15.2 per cent of the company.
It had offered the shares at 1,100-1,400 pence.
The company has more than three million registered users, and processes more than five million bets a day.
It was founded 10 years ago by Andrew Black, a one-time professional gambler, and former JP Morgan trader Edward Wray.
Goldman Sachs and Morgan Stanley were joint bookrunners while Barclays Capital and Numis were co-lead managers.