The Dolphins announced the deal on their official Twitter feed saying, "The ink is dry and it's official. Please welcome @Wallace17_daKid to the Miami Dolphins!"
The deal is worth $60 million over five years and includes $30 million in guarantees, sources told ESPN NFL Insider Adam Schefter.
Wallace, a restricted free agent, had 1,193 receiving yards and eight touchdowns in 2011 with the Pittsburgh Steelers and was selected to his first Pro Bowl. The 25-year-old has led the Steelers in receiving touchdowns the past two seasons after tying for the team lead his rookie season.
Pittsburgh changed offensive coordinators after the 2011 season, parting ways with Bruce Arians and hiring former Chiefs coach Todd Haley.
The Steelers drafted Wallace in the third round (84th overall) in 2009 out of Mississippi.
The Ellerbe deal is worth $35 million over five years, according to The Baltimore Sun.
Ellerbe was the Ravens' best defensive player by the end of the team's Super Bowl run. This season, he finished second on the team in tackles (89) and sacks (4.5).
To make way for their new acquisitions, the Dolphins released linebacker Karlos Dansby.
Dansby completed his ninth season, and third with the Dolphins, this year, finishing with a career-high 134 total tackles.
Earlier, a source said the Dolphins were attempting to sign Tennessee Titans free-agent tight end Jared Cook. However, Cook has reached an agreement with the St. Louis Rams, according to league sources.
ESPN NFL Insider Adam Schefter and ESPN.com's Jamison Hensley contributed to this report.