The Italian side, who are currently chasing a European place for next season in the Serie A, confirmed the deals on Thursday after coming to an agreement with the two clubs.
Wolski, who has three international caps for Poland and was included in the provisional squad ahead of Euro 2012, has signed a four-and-a-half year deal with the club and will wear the number 27.
The 26-year-old Compper, who has one Germany cap to his name, has put pen-to-paper on a three-and-a-half year contract and will don the number five shirt.
Compper and Wolski become the second and third additions to la Viola following Giuseppe Rossi's arrival from Villarreal earlier in the month.
Fiorentina have also secured the services of Marcelo Alejandro Larrondo this month, but he will join the team in the summer.