The club had gone stale under Arsene Wenger and were in desperate need of a new change.
He had a decent first season, but narrowly missed out on qualification to the Champions League after falling short in both the Premier League and the Europa League final.
Emery was given money to spend this summer and he wasn't afraid to use it as he brought in David Luiz, Kieran Tierney, Dani Ceballos and Nicolas Pepe.
Expectations were high when the Premier League kicked off again in August. But it's all starting to fall apart.
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Arsenal's match against Crystal Palace on the weekend was an absolute disaster.
The Gunners raced into a two-goal lead after just nine minutes but were pegged back to 2-2 to just after half-time.
To make matters worse, club captain Granit Xhaka was jeered by his own fans as he was subbed off and responded by telling them to 'f*** off'.
He then made his way down the tunnel and left the stadium before the end of the game.
Many Arsenal fans are now calling on Emery to be sacked.
Interestingly, a Twitter thread written by a Spanish football expert when Emery took over is coming to light once again following the club's recent struggles.
And everything that David Cartlidge wrote is turning out to be true.
"Overall, Emery an underwhelming appointment, doesn't really profess good or winning football. Too pragmatic, dogged by stubbornness with his systems," he began.
This has turned out to be true as Emery's football has been criticised. He doesn't play expansive football and is insistent of playing out from the back, despite this often proving detrimental.
His tactics don't even change when he plays the likes of Manchester City and Liverpool.
"Arteta was exciting due to being an unknown, the freshness of him starting his coaching career was intriguing," Cartlidge's second tweet read.
"If you don’t go down that road, you go elite. Emery is not elite, always in the rung under that. Maybe one even further below."
Very few would argue that Emery is an elite manager right now.
"Get ready for the video sessions, Arsenal players. And lots of them," he continued. "Joaquin’s famous anecdote is that ‘Emery played so many videos, I ran out of popcorn’. Can exhaust players, suck out their motivation etc."
This could also be true given Arsenal's huge downturn in form.
"Often guilty of poor in-game management," another tweet read. "Few coaches can snatch a loss or draw from the jaws of victory like Emery. Let’s not even get on to what happens when he faces teams that go down to ten men."
Sunday's result proves this statement. None of the big teams would lose against Palace after leading by two goals at home after 10 minutes.
But somehow Emery managed to find a way to not take all three points.
"In terms of discipline, we are talking about a severe lack of authority," he added. "Valencia players walked all over them, and he was not even dealing with stars.
"At PSG, notoriously passive. Wonder how long it will take Arsenal squad to figure it out."
Firstly, Emery gave Arsenal players the power to choose their own captains, which rarely happens at other clubs.
Emery then ordered Xhaka to apologise after his behaviour on the weekend but he has not listened.
The Spaniard has also had trouble controlling the team's star player, Mesut Ozil. The two fell out and now Ozil doesn't even make it into the team at all.
Cartlidge then concluded his thread by picking out more flaws in his tactics.
"The fear, the nerves, ignoring positive game plan and setting up a deep shape. All very much signs of full Emery," he wrote.
"FULL UNAI REACHED. NEVER GO FULL UNAI..."
And just how many times have Arsenal supporters had to deal with this over the past year and a half? Countless times...
You were all warned, Arsenal fans.News Now - Sport News