ESPN said that figures were boosted by coverage of the US Open Golf Championship and Euro 2008, with viewers averaging about three hours watching online.
Damon Phillips, vice president of the site, said expanded programming such as cricket would continue to stimulate "strong growth."
The 360 site offers over 2,500 live events a year and is available free to subscribers of broadband services that have agreed to pay license fees to ESPN such as Verizon DSL.
