The deal is worth $37 million with $17 million guaranteed, sources told ESPN on Wednesday. He will earn $9 million in the first year, a source told ESPN.
McLeod, 25, developed from key special-teams contributor to starting free safety by 2013 and became a staple in the Rams' secondary.
In 2015, McLeod set career highs in tackles (81) and forced fumbles (three) to go with a fumble recovery and an interception. He has 227 tackles, five interceptions, seven forced fumbles and five fumble recoveries in his career.
The Rams used a second-round tender on McLeod as a restricted free agent before last season. They originally signed him as an undrafted free agent out of Virginia in 2012.
ESPN Rams reporter Nick Wagoner and ESPN's Adam Caplan contributed to this report.