Macdonald attended the University of Georgia, where he began his coaching career as a graduate assistant in 2010. He previously served as an assistant coach for the Baltimore Ravens and at the University of Michigan.
Macdonald served on John Harbaugh's coaching staff with the Baltimore Ravens for seven seasons from 2014 to 2020.[6] He was hired as an intern in 2014 and was promoted to defensive assistant in January 2015,[7] defensive backs coach in January 2017,[8] and linebackers coach in January 2018.[9]
On January 27, 2022, Macdonald was re-hired by the Baltimore Ravens as their defensive coordinator under head coach John Harbaugh, replacing Don Martindale.[12] In 2022, Macdonald led the Ravens' defense to only allowing 315 points in 17 games.[13] Averaging just under 19 points per game, the Ravens' defense was ranked the fourth best defense in the league.[14] In 2023, the Ravens' defensive unit improved under Macdonald as they only allowed 280 points in total on the season. The Ravens would advance to the AFC Championship this season and despite losing to the eventual Super Bowl champions, the Kansas City Chiefs, the Ravens would hold the Chiefs to just 17 points, marking the team's sixth consecutive game where they held an opponent to 20 points or less.[15]
Macdonald began his inaugural season with Seattle by leading the team to three straight victories for the first time since 2020.[19] The team followed this start by going on a three game losing streak. By the Seahawks' Week 10 bye, the team held a record of 4–5, falling to last place in the NFC West.[20] The team improved to 5–5 in Week 11 when Macdonald's Seahawks defeated the reigning NFC champions and division rivals, the San Francisco 49ers, 20–17.[21] In Week 18, he led the team to a 30–25 victory against the division rival Los Angeles Rams on route to his 10th coaching win in his first season, becoming the first head coach in franchise history to reach 10 wins in his inaugural season.[22]
^"Coaching staff altered". The Baltimore Sun. January 25, 2015. p. D5 – via Newspapers.com.("The Ravens also announced the promotion of Mike Macdonald, 27, into a defensive assistant role. Macdonald was a coaching assistant last season, working primarily with the secondary. Before joining the Ravens, he was a safeties and defensive quality-control coach at Georgia.")
^"Ravens go with continuity, promote Martindale". The Baltimore Sun. January 10, 2018. p. D4 – via Newspapers.com.("Mike Macdonald, a 30-year-old who was a defensive assistant in 2015 and 2016 and defensive backs coach this past season, will be the new linebackers coach.")
^Suss, Nick (January 13, 2024). "Titans conduct head coaching interview with Mike Macdonald, Antonio Pierce". Nashville Tennessean. Michigan improved from 95th in scoring defense in 2020 to eighth in 2021, with Macdonald's defense helping lead the Wolverines to a Big Ten title and College Football Playoff berth.