Bulgaria international Mihaylov moves to the Serie A club after six years with the Eredivisie outfit.
Mihaylov spent three seasons on loan with Twente after failing to qualify for a British work permit following his move to Liverpool in 2007.
Twente signed Mihaylov on a permanent deal in 2010 and he quickly became a mainstay at De Grolsch Veste.
He joins a Verona team that has recruited extensively since securing a return to the top flight with promotion from Serie B last term, with veteran striker Luca Toni and midfielder Massimo Donati among those to link-up with Andrea Mandorlini s side.
The 25-year-old had been linked with a move to fellow Serie A newboys Sassuolo, but he will now compete with Brazilian shot-stopper Rafael for a place in the starting 11.
Milhaylov made 35 appearances for Twente last season.