Booking agreed to acquire the Swedish global flight booking company from CVC Capital Partners, the Luxembourg private-equity firm.
"As international air travel rebounds from the impact of the pandemic, we look forward to building upon our existing relationship with Etraveli Group to make the travel booking experience easier and more seamless to support our partners and customers," Booking Holdings Chief Executive Glenn Fogel said in a statement.
Etraveli Group will remain headquartered in Sweden under its current leadership.
Closing is subject to conditions including regulatory clearances.
This is Booking Holdings' second large acquisition in recent weeks. On November 12 the company unveiled plans to buy hotel wholesaler and distributor Getaroom for $1.2 billion.
In August, the Norwalk, Conn., company reported a loss of $4.08 a share, compared with a profit of $2.97 a share in the year-earlier quarter. The latest adjusted loss was $2.55 a share.
Revenue reached $2.16 billion from $630 million.
Besides Priceline, Booking Holdings operates Booking.com, Agoda, Rentalcars.com, Kayak and OpenTable.
The results reflect a year and a half of pandemic, which has devastated the travel-and-leisure industry.
Travel has been picking up -- but the delta variant of COVID-19 has recently thrown a newly forged wrench into the works.
Booking Holdings shares at last check were little changed near $2,343. The stock has traded on Wednesday off as much as 2.1% at around $2,291.