Yates, a graduate of Boise State, was an assistant coach with the Broncos from 2003-11, and has been the co-defensive coordinator at Texas A&M the last two seasons.
Harsin announced Tuesday that Scott Huff and Andy Avalos, also graduates of Boise State and current assistants with the Broncos, would return for next season.
"Being able to bring a coach, and person, of high quality like Marcel to our program is a home run," Harsin said. "We worked and played together at Boise State, and he is one of the sharpest defensive minds in the country.
"Marcel has always connected with his players and is an outstanding recruiter. During his two years at Texas A&M he has developed great recruiting ties to the state of Texas and throughout the SEC."
Yates, who played defensive back for the Broncos from 1996-99, was Boise State's cornerbacks coach from 2003-05, before taking over the entire secondary from 2006-10. He added defensive pass game coordinator responsibilities in 2011, before moving on to Texas A&M.
"It's an honor for me and my family to come back to Boise State," Yates said. "As excited as I am, I understand I have big shoes to fill. Coach Petersen and his staff have left Boise State in a great position, and I am elated about the opportunity to help continue this success.
"The last two years at Texas A&M have been great. I've learned so much from Kevin Sumlin (Texas A&M Head Coach) and Mark Snyder (Texas A&M Defensive Coordinator). Coaching in the SEC was a great experience. I would like to thank them both for the opportunity to grow as a man and as a coach."
While with the Broncos as an assistant, Boise State won seven conference championships in nine seasons and appeared a bowl game each year. The Broncos won five of the bowl games, including both the 2007 and 2010 Tostitos Fiesta Bowls.
During his final six seasons with Boise State, five defensive backs went on to be selected in the National Football League Draft: Gerald Alexander (Second Round, Detroit Lions, 2007), Orlando Scandrick (Fifth Round, Dallas Cowboys, 2008), Kyle Wilson (First Round, New York Jets, 2010), Brandyn Thompson (Seventh Round, Washington Redskins, 2011) and George Iloka (Fifth Round, Cincinnati Bengals, 2012).
He also coached Jamar Taylor, who was selected in the second round of the 2013 NFL Draft by the Miami Dolphins.
In his first season with Texas A&M, the Aggies concluded the season ranked fifth-nationally in both the Associated Press and USA Today Coaches Polls, and won 11 games for the first time since 1998. This year the Aggies rank No. 20 in the AP Poll and No. 21 in the Coaches Poll.
Prior to joining the Boise State staff, Yates was an assistant secondary coach at Montana State from 2001-02. In his second season with the Bobcats, Montana State won its first Big Sky Conference Championship and earned its first NCAA Division I-AA Playoff appearance in 18 years.
Yates earned his bachelor's degree in social science from Boise State in 2000. Following his senior season, he earned the team's Denny Erickson Award for Valor.
Former Boise State quarterback Mike Sanford has been named the Broncos' offensive coordinator and quarterbacks coach, head coach Bryan Harsin announced Wednesday.
Sanford, who has spent the last three seasons as an assistant coach at Stanford (2011-13), played for Boise State from 2000-04.
"I tried to hire Mike last year at Arkansas State and feel fortunate we are able to bring him back to Boise," Harsin said. "Mike is a young, bright coach, and having played the quarterback position at Boise State, he has a great understanding of what we are trying to do. Mike has built up a great coaching background since his playing days as a Bronco, and I look forward to building the offense with him."
"I'm extremely excited about the opportunity to return to my alma mater, which I've always believed to be one of the elite football programs in the country," Sanford said. "This is a great time in the history of Boise State's storied program and I cannot wait to work alongside Coach Harsin and the rest of the new staff. I have a tremendous amount of respect for Coach Harsin as a person and as a football coach. My family cannot wait to return to one of the best places to live in the country."
Sanford began his career with the Cardinal as the team's running backs coach in both 2011 and 2012. He coached quarterbacks and wide receivers in 2013, and has been Stanford's recruiting coordinator each of the last two seasons.
The Cardinal won the Pac-12 Championship in both 2012 and 2013, and will be making a second-straight appearance in the Rose Bowl. Stanford also played in the Tostitos Fiesta Bowl during Sanford's first season.
This season, under Sanford's tutelage, Cardinal quarterback Kevin Hogan ranks 19th-nationally in passing efficiency (154.1). Sanford also worked closely with Cardinal running back Stepfan Taylor, who broke the school's career rushing record in 2012, a mark that had stood since 1981.
The Cardinal ranked 18th-nationally in rushing in 2011 (210.6), a major reason Stanford finished the season ranked seventh-nationally in scoring (43.2) and eighth-nationally in total offense (489.3).
Following his playing career with the Broncos, Sanford served as a graduate assistant with UNLV from 2005-06, where he worked with his father, Mike, then the head coach of the Rebels. He moved on to Stanford, where he was an offensive assistant from 2007-08.
His first full-time coaching stint came at Yale in 2009, where he coached tight ends and fullbacks and served as the team's recruiting coordinator.
The following season (2010) he coached quarterbacks and was the passing game coordinator at Western Kentucky.
Sanford earned his bachelor's degree in political science from Boise State in 2005.