When Cooper took over at the City Ground in September, Forest were bottom of the Championship having lost six of their first eight games.
But Sunday saw him lead his side into the playoff final at Wembley, having overcome Sheffield United over two legs after a penalty shootout win in Nottingham.
Huddersfield with the opposition at Wembley, and it was a controversial clash as the Terriers were denied two strong penalty claims despite the availability of VAR for the playoffs.
Ultimately, the final was decided by a Levi Colwill own goal, with Forest winning 1-0 and securing their place back in the Premier League.
Forest, for a long time a staple of the top flight, were last in the Premier League in 1998/99 – that relegation being their second in three seasons, consigning them to 23 years in the lower leagues.
It serves as the next step in an impressive career for Cooper, who began coaching with Wrexham in 1998 before moving to Liverpool’s academy in 2008.
He spent five years at Kirkby, working with the likes of Harry Wilson, Sheyi Ojo, Jordon Ibe and Ryan Kent during a stint in charge of the under-18s, while he has been credited with overseeing the development of Trent Alexander-Arnold and Raheem Sterling.
After that came five years in the England setup, leading a side including Rhian Brewster, Phil Foden, Jadon Sancho, Emile Smith Rowe, Conor Gallagher, Marc Guehi and Morgan Gibbs-White to glory at the U17 World Cup in 2017.
Then, following a glowing two years with Swansea, Cooper made the jump to Forest last year and has surpassed expectations in Nottingham.
Forest, who lost to Liverpool in the FA Cup quarter-finals in March, were transformed into a talented young side featuring the likes of Brennan Johnson and loan duo James Garner and Djed Spence.
Johnson, the 21-year-old Welsh winger, ended the season as top scorer with 19 goals in 53 appearances, while Middlesbrough right-back Spence has attracted interest from number of clubs including Liverpool during his loan spell at the City Ground.