Henry is inheriting a team the relegation zone of Ligue 1 with only one win and six points, something that would have seemed impossible 18 months ago.
Wind the clock back to then and the club had won the league and as one of the most exciting side's in Europe, reached the semi finals of the Champions League, so how have Monaco got into this mess?
Football writer Tom Williams, in a feature in 'Sky Sports' has tried to explain."Basically that entire team has been taken to pieces," he says.
"The only first-team players from the title-winning squad who are still there are Danijel Subasic, Djibril Sidibe, Jemerson, Kamil Glik and Radamel Falcao. The entire midfield from that team has gone.
"In recent years Monaco have adopted a business model whereby they invest heavily in young, up-and-coming talent, groom them into top-level professionals and then sell them on at a profit. They did that throughout Leonardo Jardim's time at the club and, generally speaking, it's been very successful.
"But they'd been walking a bit of a tightrope in terms of balancing the sales and purchases of players and the general feeling is that, in the most recent transfer window, they fell off it.
"The average age of the players they signed was even lower than usual and to make matters worse, a lot of the players they signed after the title win in 2017 still haven't settled in.
"Youri Tielemans, so far, has been a major disappointment, Stevan Jovetic has barely been fit and Keita Balde went back to Italy after only one season.
"They've also been unlucky with the players they signed this summer. Aleksandr Golovin, who was so impressive at the World Cup, got a big injury in his first training session and has only just started playing. Nacer Chadli looks well short of fitness.
"And to compound matters, the defensive stalwarts of the title win - notably Glik and Jemerson - are struggling for form, Subasic and Sidibe have had injury problems and Falcao has been off the boil for the best part of six months.
"So they've got an undercooked, inexperienced squad in which the more experienced elements are either a) still settling in, b) injured or c) out of form. It's a bit of a perfect storm really!
"Jardim predicted before the season had even started that this would be his most difficult season at Monaco and he wasn't wrong!"
However Williams does not think all is lost: "If Henry can get Golovin, Chadli and Stevan Jovetic fit and firing, if he can help Tielemans to raise his level (and he's worked with him already with Belgium) and if he can help Falcao find some form, Monaco could do some damage."
What's for certain is that the former Barcelona man has taken on a massive challenge, but it could be one which he is equal to.