Valve's The International Dota 2 Championships was watched by over 20 million unique viewers online, says the developer.
Peak concurrent online viewers was over 2 million, "more than doubling last year's peak", said the company in a short and snappy announcement on Tuesday.
Valve's The International Dota 2 Championships was broadcast live via US TV sports network ESPN.
The International Dota 2 championship took place at the KeyArena in Seattle, Washington on July 18-22, hosting 11 of the best competitive DotA teams, as well as four regional qualifiers.
Dota 2 players competed for a share of more than $10 million - a record for a pro gaming league event, smashing last year's then record-setting prize pool of just under $2.9 million.
Valve contributed an initial $1.6 million to the prize pool. It also added 25 percent of the purchase price of Compendiums and related in-game goods to the pool, letting players contribute to the share.