The deal is worth $80 million, a source told Adam Schefter of ESPN, meaning he's due $88 million from L.A. over the next six years.
Although the Rams have yet to confirm financial terms of the extension, Cooks will reportedly get $50.5 million guaranteed with $20.5 million guaranteed upon signing, Ian Rapoport of NFL Network reports.
Cooks, one of the most prolific deep threats in the NFL, was acquired from the New England Patriots via trade in April. The 24-year-old caught 65 passes for 1,082 yards and seven touchdowns last year, and has gone over 1,000 yards receiving in three straight seasons.
"Brandin Cooks has shown himself to be a class act on and off the field since the first day he joined our team," Rams head coach Sean McVay said in a news release. "He's a proven professional in this league and signing him to a long-term contract was always our goal. We're excited to keep Brandin in a Rams uniform through 2023."
Cooks was one of several high-profile acquisitions the Rams made this offseason. The speedster broke into the league as a first-round pick of the New Orleans Saints in 2014 and spent three seasons in the Big Easy before being traded to New England ahead of the 2017 campaign.