Castagne is set to arrive at the King Power Stadium on a five-year deal for a reported fee of £18.5 million, with add-ons expected to push the price up to £23 million, and will provide much-needed competition in the left-back role following the departure of Ben Chilwell to Chelsea.
Due to the 24-year-old's international commitments with Belgium, Castagne will have to wait until next week at the earliest before he meets his new teammates but is likely that Leicester will confirm his arrival before he joins up with the first-team squad.
"I like Leicester's style"
Whilst the club are yet to provide official confirmation, Castagne himself has expressed his excitement to swap Serie A for the Premier League.
Speaking to Belgian public service broadcaster RTBF on Tuesday, the seven-time capped international stated that it has always been a dream to play in England's top-flight and that conversations with Leicester boss Brendan Rodgers helped convince him to join the Foxes.
Castagne said: "It has always been my dream to play in the Premier League. It was my priority league over other offers.
“I also like Leicester's style of play which should suit me. And the feeling with the manager is very good, he contacted me regularly."
What can Castagne offer?
The first word that comes to mind with Timothy Castagne is versatility.
His ability to operate on both the right and left hand side of defence in either the full-back or wing-back position is a major asset to Leicester ahead of what is likely to be a busy season with the extra pressure of European football this season.
Last season for Atalanta, the 24-year-old featured 33 times in all competitions as the Italian side finished third in the league and went as far as the quarter-finals of the Champions League in their first appearance in the competition.
In that run, Castagne played as a right-wing back and left-wing back almost identically, with 15 appearances on either flank - and three more as a left-back in a flat back four - providing the Nerazzurri with two goals and three assists in another memorable campaign.
What does this mean for Leicester's formation?
There is every chance that the signing of Castagne means that Brendan Rodgers will use a three-at-the-back formation this year.
The Belgian is right-footed so could play right wing-back and allow James Justin to play on the left-hand side whilst the Foxes' first-choice Ricardo Pereira continues his recovery from injury.
Alternatively, Rodgers may revert back to a four-man defence where Castagne operates as the main left-back with youngster Luke Thomas tipped for a potential loan move away, and the experienced Christian Fuchs only considered a back-up these days.
Rodgers however has the luxury of knowing that Castagne is a reliable performer on either side of the pitch, and will be a more than adequate replacement for his former Fox Ben Chilwell.