Bird has been a stalwart of Formula E since its inception in 2014, driving for Virgin Racing, Envision Racing and more recently Jaguar over the last nine years.
The 36-year-old spent the last three seasons with the British manufacturer, scoring two wins during the first of those campaigns in Diriyah and New York.
But Bird's form fell away this season as he failed to score a win and finished eighth in the drivers' standings, while also being at fault for colliding with team-mate Mitch Evans on two occasions.
The Briton's spot at Jaguar for next season has been taken by Nick Cassidy, with Bird strongly linked to a McLaren switch which was finally confirmed on Tuesday.
"I'm super excited to get going with the McLaren Formula E Team. Becoming part of a team with so much heritage and prestige as the McLaren Racing family feels special," said Bird, a winner of 11 E-Prix.
"We know there is some work to do ahead of Season 10 to ensure we get to where we want to be, which is at the front of the Formula E pack.
"It feels great to be part of the team and I can't wait to kick off the season preparations. I'm super motivated and driven to deliver success with the team in Season 10."
McLaren joined Formula E this term after essentially taking over Mercedes' entry, the German manufacturer having withdrawn from the championship after claiming two teams' and two drivers' titles on the bounce with Nyck de Vries and Stoffel Vandoorne.
Briton Jake Hughes impressed during his rookie season with McLaren, taking two pole positions and finishing 12th in the drivers' standings, eight points clear of Rast who secured the team's only podium with third in Diriyah.
Hughes was confirmed as having re-signed with McLaren last week, while BMW-contracted sportscar racer Rast would be leaving the squad after just one season.
Zak Brown, McLaren Racing's CEO, said: "It is a pleasure to welcome Sam to the McLaren Racing family.
"Throughout his time in Formula E, Sam has proven himself to be an impressive talent, and we are eager to leverage his experience and expertise to help bring the McLaren Formula E Team further success in Season 10.
"Alongside Jake, I'm confident that we have one of the strongest pairings on the Formula E grid."
