After a goalless first half, Barella put Italy ahead in the early stages of a the second period with a sweetly struck volley. Berardi added a penalty to double the lead for Roberto Mancini's team.
Belgium caused a scare for Italy late on as Charles De Ketelaere goat a goal back, but Italy held on to secure victory.
Nicolo Barella celebrates after his goal put Italy in the lead during their clash with Belgium
Barella scored a sweetly-struck volley in the early stages of the second half to open the scoring
Domenico Berardi slotted home a penalty in the 65th minute to make it 2-0 to Italy
Belgium struck the crossbar in each half, first through Alexis Saelemaekers and then Michy Batshuayi, and Yannick Carrasco hit the post.
Both teams contained talented players but some key individuals were named on the bench, such as Jorginho for Italy and Kevin de Bruyne for Belgium.
Italy were beaten by France in the semi-finals, while Belgium lost to Spain in an enthralling encounter.
Roberto Mancini's side started very brightly, with the highly regarded Federico Chiesa having a shot blocked before shooting over the crossbar shortly afterwards.
Belgium goalkeeper Thibaut Courtois got a touch to the ball but he couldn't keep it out
The Italy players were delighted after taking the lead in the Nations League play off semi-final
Substitute Charles De Ketelaere managed to get a goal back for Belgium in the closing stages
Belgium were without star striker Romelu Lukaku due to muscle fatigue, so Michy Batshuayi started up front and he had his