The 20-year-old joins the Seasiders following the expiration of his contract at Sutton United.
Kouassi has penned a three-year contract at Bloomfield Road, with an option of an additional 12 months in the club’s favour.
“This is the next big step in my career, and I want to take it with both hands,” the forward told the Seasiders’ official website.
"I want to be a part of the journey this Club is on, and show exactly what I can do on the pitch.
“I’ve spent some time here during pre-season and have met the rest of the squad.
"There is a really strong culture here, and with the talent that is already here, I feel I can develop my own game and continue to improve as a player.”
Kouassi came through the youth system at Sutton, and made his senior league debut in 2022.
He has also picked up experience while on loan with Bedfont Sports, Hampton and Richmond Borough and Chesham United.
On the signing, Neil Critchley said: “We want to be a club that provides opportunities for young players to develop their potential, and we feel Kylian will be able to do that here with us.
“After gaining experience in the EFL last season in League Two, we believe he has the attributes to make the next step in his career.
“He impressed us all in a short spell with us during pre-season, and we are really looking forward to helping him become a Blackpool player in the future.”
Kouassi is the Seasiders’ second signing of the day, following the arrival of Jordan Rhodes.
The experienced striker has made the move to Bloomfield Road on a season-long loan from Huddersfield Town.
The 33-year-old has a good record in League One, and holds the record for the most goals in a singular campaign at this level.
Rhodes started his professional career with Ipswich, and has gone on to play for the likes of Blackburn Rovers, Middlesbrough and Sheffield Wednesday.
He has also enjoyed two stints with Huddersfield, whom he joins the Seasiders from.
It was during his first stint at the John Smith’s Stadium, he took League One by storm, with 36 goals throughout the 2011/12 season.