In 1998, he was appointed SG's responsible for foreign affairs as well as vice president of the International Union of Socialist Youth (IUSY), of which he was elected secretary general in 2001.

[2] In 2006, Amendola was appointed in the national secretariat of the Democrats of the Left, and in November 2006, he was elected regional secretary of DS for Campania.

[9] On 29 January 2016, Amendola was appointed undersecretary to the Ministry of Foreign Affairs in Renzi's cabinet, a position that he held until 1 June 2018, serving under the premiership of Paolo Gentiloni too.

[12] In August 2019 tensions grew within the populist government, leading to the issuing of a motion of no-confidence on Prime Minister Giuseppe Conte by the League.

[13] After Conte's resignation, the national board of the PD officially opened to the possibility of forming a new cabinet in a coalition with the M5S,[14] based on pro-Europeanism, green economy, sustainable development, fight against economic inequality and a new immigration policy.