The Sky Blues have been operating under a transfer embargo since the start of March but manager Steven Pressley has finally been able to bring in a new face to bolster his threadbare ranks.
City have not yet fully exited the embargo but they have now been granted permission to sign players under the League's supervision.
Development director Steve Waggott explained: "I've been working with the Football League to move things forward while issues around embargo and administration are resolved.
"We now have an arrangement in place where we can bring a player in under certain circumstances - depending on cost and on players moving out.
"Ultimately, the Football League are not going to allow us to go out and sign who we want, when we want until the embargo is lifted but this does at least give us some room for manoeuvre."
Former Reading striker Manset, a free agent, is the first player to arrive, penning a one-year deal with a further 12-month option.
And Pressley is delighted to have landed the 23-year-old Frenchman, who has been on trial with the club for the past month.
Pressley said: "Mathieu is a player we have been looking at for a while and we have been delighted with the levels he has shown during pre-season with us.
"He is a very exciting player and at the age of 23 he is a player I believe is still to fulfil his huge potential. I believe at this club we will give him the opportunity to do so.
"It's always a real boost to the squad when a new player joins the team."
Manset is in contention to make his debut in Sunday's clash against Bristol City - Coventry's first 'home' fixture at Sixfields Stadium as they prepare to groundshare with Northampton for the next three years while their proposed new stadium is built.
The Sky Blues left the Ricoh Arena at the end of last season following a lengthy rent row with stadium management company Arena Coventry Limited (ACL).
Last Friday, the Sky Bet League One club were hit with a 10-point deduction after the Football League transferred their Golden Share to the Otium Entertainment Group, with Coventry City Football Club Limited facing liquidation after a Company Voluntary Agreement (CVA) could not be agreed with creditors.
As far as the League is concerned City have now exited administration, although that is not quite the case within business terms as CCFC Ltd prepares to go into liquidation.