Zappacosta was born in Sora (Frosinone) on 11th June 1992. He spent his youth career playing with Sora, Isola Liri and Atalanta before making the jump to Avellino, where he became one of the best full-backs in Serie B. He impressed whilst playing with Avellino that Atalanta decided to call him back. He played his first Serie A game on 31st August 2014. In 2015, he moved to Torino where he was a regular for two years before moving to his current club Chelsea in England.
He was called-up for the Under-21 team for a crucial European Championship qualifier against Belgium, which took place on 5th September 2013. Under-21 Italy coach Di Biagio was convinced of Zappacosta performance and decided to call him up for further games. Zappacosta was one of the key figures in qualification to the European Championship in the Czech Republic.
Called up to the training squad ahead of Euro 2016 by Antonio Conte, he made his full international debut under Gian Piero Ventura on 12th November 2016 as Italy beat Liechtenstein 4-0 in a World Cup qualifier.