Tucker's six-year contract with the Spartans, which was formally approved by the university's board late Wednesday afternoon, is worth approximately $30 million.
"It brings me great pleasure to welcome Mel Tucker to the Spartan family as the 25th head coach in Michigan State football history," athletic director Bill Beekman said in a statement released by the school. "Mel brings a championship pedigree, NFL experience, connections to our region, success on the recruiting trail and head coaching experience to our program.
"Beyond his impressive list of credentials is an even more impactful leader of men with an energetic personality that will pay dividends on the recruiting trail. Perhaps more importantly, he'll connect with our student-athletes to help them develop beyond just their skills on the football field. His attention to detail will leave no stone unturned in his drive for championships."
Tucker began his coaching career at Michigan State as a graduate assistant for Nick Saban in 1997.
"It is a blessing and honor to return to Michigan State University where I began my coaching career with Nick Saban," Tucker said in the statement. "... Returning home to Michigan State is a once in a lifetime opportunity for me and my family but it created the toughest decision of my life -- to leave Colorado."
Tucker resigned as the Buffaloes' coach after one season in which the team went 5-7. Last week, he finalized the nation's No. 34 recruiting class, according to ESPN.
Sources told ESPN that Tucker went to the Colorado facility Wednesday morning and wanted to address the team before departing for Michigan State but was informed he could not do so. Athletic director Rick George said at a news conference Wednesday that Tucker did not address the team before resigning.
To all Spartans, please welcome Coach Mel Tucker to Michigan State! pic.twitter.com/irYiYfOntE— Michigan State Football (@MSU_Football) February 12, 2020
Tucker, 48, will replace Mark Dantonio, who announced his retirement last week after 13 seasons at Michigan State. Dantonio, 63, went 114-57 with the Spartans, winning or sharing three Big Ten championships and reaching the College Football Playoff in 2015. He left as Michigan State's winningest coach but also is facing a lawsuit from former recruiting director Curtis Blackwell, who alleges that Dantonio committed multiple NCAA violations.
"Mel is charismatic, brings good energy, and is a very forward thinker," Dantonio said of Tucker's hire on Wednesday. "He's also an outstanding recruiter who connects with his players, but also holds them accountable. He's from the Midwest and has a Spartan background with knowledge of the Big Ten."
Tucker was one of several candidates seemingly to turn down Michigan State's initial overtures, and he tweeted Saturday that he remained committed to Colorado after speaking with MSU about its vacancy. However, Michigan State offered more resources beyond annual salary.
"It's fitting that Mel returns to the place where his coaching career began as a graduate assistant," Beekman said. "While he returns to Michigan State with a loftier title, his passion is every bit as fierce. Head football coach might be his title, but he will be an amazing ambassador for our department, our university and more than 550,000 living alums."
A Cleveland native who played defensive back at Wisconsin, Tucker was a defensive coordinator for three NFL teams and served as the Jacksonville Jaguars' interim head coach in 2011, going 2-3. Tucker worked alongside Dantonio at Ohio State from 2001 to 2003 and held coordinator jobs at Ohio State and Georgia before landing his first head-coaching opportunity at Colorado.
Colorado said a search for a new coach is already underway.
"We are disappointed to see Coach Tucker leave," George said in a statement Wednesday. "We are excited about the upward trajectory of our football program and we'll get to work immediately hiring the next head coach to build on our momentum and lead our young men. We're confident this program is on the verge of competing at the highest level and has the resources and support in place to do so for a long time."