Fresh after being named in the EFL Championship Team of the Year, Mooy received further praise from his club coach.
"He's one of the best [signings] for sure," Wagner told the Huddersfield Daily Examiner.
"We are very happy with him on the pitch and in the dressing room as well.
"He is an interesting character because he is very quiet but always focused, and he is a great footballer as well.
"We are very happy that we have him."
The midfield maestro, currently on loan at the Terriers from Manchester City, has been a revelation for third-placed Huddersfield and a vital part of their push for promotion to the Premier League.
Mooy has played 39 matches for Huddersfield this season, scoring three goals and providing five assists.
However, It has been the 26-year-old's incredible passing stats, including an average of 71.9 passes per match and 2.1 key passes per game, which has truly made him stand out as one of the Championship's best.
Currently in camp with the Socceroos in Tehran ahead of Thursday's clash with Iraq, Mooy will be determined to replicate his club form as Australia battles to secure World Cup qualification.