The Hammers are building a Little Italy in London with two signings from Serie A in one day after several days of negotiations.
Borriello is well-travelled in his career, playing for the likes of Milan, Genoa, Juventus, Sampdoria and Roma.
The 28-year-old Nocerino has been capped by his country on 15 occasions, going to the 2008 Beijing Olympics and Euro 2012, where he scored one of the penalties that knocked out England at the quarter-final stage.
Born in Naples, Nocerino's career began at Juventus, where he played 32 league games, as well as gaining experience with loan spells at the likes of Genoa, Messina and Piacenza.
He moved on to Palermo in 2008 and went on to establish himself at the Sicilian club in a three-year spell which yielded 106 league outings and six goals.
After helping the Rosanero qualify for the UEFA Europa League, Nocerino left for AC Milan in the summer of 2011, making his UEFA Champions League debut shortly afterwards when Milan drew 2-2 with Barcelona.
His first goal for Milan came against his former club Palermo, and a successful first season at the San Siro also included a hat-trick in a 4-1 victory over Parma.
The Neapolitan notched eleven goals in all in the 2011/12 campaign and backed that up with a further 31 appearances last term.