Belgian midfielder Mangala becomes the seventh player Everton have brought in this summer and replaces his international team-mate Amadou Onana who left for Aston Villa earlier in the window.
It has been a busier than expected transfer window for the Blues - at least in terms of in-comings - with most of the pre-summer speculation surrounding who would leave the club.
As well as Onana, of the first-team squad the Toffees have sold Lewis Dobbin - also to Villa - and Ben Godfrey to Atalanta while a number of youth team players have gone too.
Perhaps most importantly though, Everton have kept hold of Jarrad Branthwaite, despite Manchester United's relentless interest and repeated attempts to prise him away.
Dominic Calvert-Lewin also looks likely to stay put, although a late, last-minute deal could still happen of course.
So, given all the financial constraints, chaos and uncertainty over the club's ownership that Sean Dyche and Kevin Thewell were operating under, it looks like decent business overall in the transfer window.
On paper at least the Toffees squad looks a little deeper and has more quality - at least up front anyway - than at the end of last season.
Of course injuries can sabotage the best laid plans and Everton still have one of the weaker and smaller squads in the Premier League and so can ill-afford injuries to key players.
Mangala's arrival provides more competition and cover in one area of the team that Dyche felt needed shoring up.
In midfield he has veterans Idrissa Gueye and Abdoulaye Doucoure plus younger players in James Garner and Tim Iroegbunam and now Mangala too.
The former Nottingham Forest player will hopefully add some extra quality on the ball and as well, a little bit more steel in the engine room.
Mangala is unable to play tomorrow as the Blues face a huge early season clash at Goodison Park against Bournemouth with three points surely a necessity.
So, it looks as though this is the squad Dyche must work with, at least until January anyway.
His task now is to find a way to improve confidence and form quickly - starting with Saturday's match - as another long, hard Premier League season looms ahead.