Robinson's agents, the Katz Brothers, confirmed the news Thursday on Twitter.
Robinson, 28, adds needed depth and experience to a receiving corps that earlier this offseason lost receiver Allen Robinson to the Pittsburgh Steelers in a trade after he spent only one season with the team.
Following a disappointing 5-12 campaign, the Rams return 2021 NFL Offensive Player of the Year Cooper Kupp, who missed the final eight games last season after undergoing ankle surgery, fourth-year pro Van Jefferson and third-year pros Tutu Atwell and Ben Skowronek.
Demarcus Robinson is entering his eighth NFL season and has 193 career receptions for 2,137 yards and 16 touchdowns.
A fourth-round pick in 2016, Robinson played six seasons with the Kansas City Chiefs, contributing 32 catches for 449 yards and four touchdowns to the 2019 Super Bowl champion team. Last season, Robinson played 17 games with five starts for the Baltimore Ravens, catching 48 passes for 458 yards and two touchdowns.
The Rams conclude voluntary organized team activities Thursday and open mandatory minicamp June 13.