Mr. Sepso, who attended Babson College in Wellesley, Mass., and Mr. DiGiovanni, who studied film at the Tisch School of the Arts at N.Y.U., were among that early class of techies who made a profit in the city’s first Internet boom. Near the turn of the millennium, however, they sensed that the bubble was about to burst and sold their company, escaping into exile to live off their earnings and play video games. Late one night, they found themselves at a bar and, wearied by the scene, decided to go home and play Xbox. A handful of acquaintances went with them — stockbrokers, barflies and their girlfriends.

“It was a bunch of late 20s, A-type, New York personalities sitting in a room, competing over video games,” Mr. Sepso said. “Sundance and I had the same thought. If we’re here doing this, then there have to be others who are out there doing it, too.”

Within months, they had persuaded the owner of a Chinatown nightclub, Fun, to let them project video games on a wall above the dance floor for spectators to watch; eventually they developed an underground following in the local gaming world.

This was at a moment when Mr. DiGiovanni started hearing rumors about secret gaming tournaments held on college campuses around the country. He and Mr. Sepso hit the road, visiting these tournaments on a kind of learning tour. “They were totally unorganized,” Mr. DiGiovanni said. “And we had some money left from our first business, but it was quickly running out. So I told Mike, ‘If we’re really going to do this, let’s do it now.’ ”

Major League Gaming was established that same year, and for its first four seasons it was kept afloat exclusively through financing from its founders. Then, in 2006, Oak Investment Partners, a local venture capital firm, gave the pair money, and by 2012 it had invested nearly $60 million in the league. While Mr. Sepso refused recently to discuss the company’s revenues, he said that this year would be its best in terms of total earnings. “It’s the first full year that we’ll be profitable,” he said.

As with any digital concern, M.L.G.’s worry from the start was how to make money from its growing traffic on the Internet. Seventy percent of its revenue comes from advertising, Mr. Sepso said. As might be expected, from the beginning, game developers, both large and small, bought advertising on the site. But in a testament to the league’s core audience — boys with wealthy parents and their own disposable income — mainstream entities like carmakers, soft-drink companies and the United States Army started to arrive.