Tom Pelissero of NFL Media reports that the 49ers also receive LB Kiko Alonso in the trade.
Jason Fitzgerald notes that the Saints should owe Alexander $3 million for the remainder of the season and will save around $900,000 by including Alonso in the deal.
The 49ers had reportedly been shopping Alexander in potential deals dating back to this offseason. However, it took until now for them to find a trade partner.
In total, Alexander spent a year and a half in San Francisco, but had been limited due to injury.
Alexander, 26, is a former fourth-round pick of the Buccaneers back in 2015. He played out the final year of his four-year, $2,758,320 contract before agreeing to a four-year contract worth $54 million with the 49ers in 2019.
In 2020, Alexander has appeared in five games for the 49ers and recorded 30 tackles, one sack, and a forced fumble.
Alonso, 30, is a former second-round pick of the Bills back in 2013. The Bills traded to the Eagles in return for RB LeSean McCoy back in 2015.
From there, Alonso was traded to the Dolphins along with Byron Maxwell back in 2016 in return for a first-round pick. Miami later traded him to the Saints for OLB Vince Biegel at the start of the 2019 season.
Alonso agreed to a restructured contract in March that will pay him a $1.7 million base salary and $1.45 million roster bonus that is fully guaranteed on the fifth day of the league year. He also gets $4.7 million in incentives that is dependent on playing time and being active for 10 or more games.
In 2019, Alonso appeared in 13 games for the Saints and recorded 31 tackles, no sacks or interceptions and one pass defense.