"We are grateful and humbled for this opportunity and could not be more excited to be the head football coach at Duke University," Diaz said in a statement. "... Duke University is an elite institution in every facet, and we are excited to be a part of it. I'm beyond excited to get to work."
Duke, which conducted finalist interviews in Las Vegas this week, has scheduled an introductory news conference for Saturday.
Diaz is coming off a season in which he led the nation's top statistical defense, as the Nittany Lions held opponents to 223.2 yards per game -- the best single-season defensive performance in the sport since Alabama in 2011.
He also brings head-coaching experience in the ACC, as he led Miami to three bowl-eligible seasons during his time there from 2019 to 2021.
Diaz, whose 2020 Miami teami was ranked as high as No. 7 in the country, was fired after three seasons with a 21-15 record. Miami is 12-12 since his departure.
He will take over a Duke program that got an energy jolt during Mike Elko's two seasons as coach. Elko went 9-4 in 2022 and led the Blue Devils to the school's highest national ranking, No. 16, this year. He left last month for the head-coaching job at Texas A&M.
"As our process unfolded, it became abundantly clear that Manny Diaz is the right fit for Duke University," athletic director Nina King said in a statement. "Manny's previous experiences have prepared him for this opportunity, and he is, quite simply, an outstanding football coach who will capitalize on the positive momentum of this program.
"An elite communicator and collaborator, Manny possesses the dynamic ability to cultivate impactful relationships with internal and external constituents surrounding a successful football program. As Duke's head football coach, I am confident that Manny will lead the young men in our program to reach and surpass their aspirations of achievement both on and off the field."
Diaz will need to work quickly to retool Duke's roster, which was laden with veterans -- the team is expected to lose well over half of its starters to graduation. Star quarterback Riley Leonard is in the NCAA transfer portal and took a visit to Notre Dame this week.
Diaz brings extensive experience in the ACC. In addition to his time at Miami as head coach and defensive coordinator, he has also had stops at Florida State as a graduate assistant and at NC State in various roles for six seasons early in his career.
After his departure from Miami, Diaz made quick work of building Penn State into a defensive power. The Nittany Lions have held opponents to 24 or less points in 17 straight games -- the nation's longest active streak.
Diaz was a semifinalist for the Broyles Award, given to the nation's top assistant, in his first season at Penn State. He'll bring extensive recruiting connections from his various other stops -- Middle Tennessee, Mississippi State, Texas, Louisiana Tech -- and a high-energy approach to recruiting.
Duke plays Troy in the Birmingham Bowl on Dec. 23.