ESL has confirmed via its website the acquisition of the ESEA platform for an undisclosed fee.
The deal will not affect ESEA's operations as the company will continue to be run as an independent entity, benefiting, however, from the products and services provided by ESL, which is owned by Swedish digital entertainment company MTG.
ESEA and ESL have long been working together, with the partnership resulting in a joint intercontinental CS:GO league, currently in its second season.
ESL and ESEA are now formally owned by MTG
ESL had long been interested in strengthening its position in North America, where it will host two events in the next three weeks: IEM San Jose, which kicks off tomorrow, and the offline finals of the ESL ESEA Pro League, from December 10-13.
"It's no secret that esports is booming, and this was a necessary step in order for ESEA to remain relevant as larger companies enter the gaming landscape," ESEA co-founder and CEO Eric "lpkane" Thunberg said in a statement.
"In choosing ESL, both a long-time partner and one of the founding companies of esports, I'm confident that ESEA will be in good hands for years to come.
"ESEA has been an incredibly fun ride. I'm immensely proud of both what we've built over the past twelve years, as well as the extremely loyal and close-knit community that's grown up with us along the way - your support did not go unnoticed."
The move is part of MTG's expansion into the esports business, which began in July when it acquired a 74% stake in ESL for €78 million.
Earlier in the month, the Swedish company acquired 100% of DreamHack AB for an enterprise value of SEK 244 million ($28 million), which means that it now formally controls three major players in the Counter-Strike scene.