The 26-year-old centre-half, who can also play in central midfield, has put pen to paper on a one-year contract with the option of another year following the expiry of his deal with Vestsjaelland.
Fleetwood boss Graham Alexander told his club’s official website: “Eggert is someone we met towards the end of last season and he came across to Fleetwood to have a look at the stadium and our training ground at Fylde at the time.
“We’ve had to be patient with a couple of players we’ve tried to recruit this summer and that’s been the case with Eggert.
“He’s come across to have his medical and sign the papers, and we’re really pleased to get him on board because he’s a very good player.
“He can play at centre-half or in midfield, and has previous experience of the British game with Hearts in Scotland and later Wolverhampton Wanderers in England.
“We feel we’re getting a good player at a good age who fits the profile of what we’re looking to do. We believe we can both be good for each other.”
Jonsson has made over 150 appearances in British football with previous clubs Hearts, Wolves and Charlton.