The midfielder was sold by Aston Villa last month.
“The Italian League suits me, even if it's difficult, but then I like challenges," Veretout said in the Press conference.
“Fiorentina are a great team and I'm looking forward to a great adventure. When I learned the Viola were interested in me I never had any doubts.
“Obviously I need to improve in helping the team and in terms of quality. Physically I've already grown because I played in the Premier League, but I need to improve in a lot of other aspects.
“The national team? I'm here to do my best for Fiorentina, then we'll see what happens with the national team in future."