He was elected to the European Parliament in 1984, and then re-elected in 1989, to the lists of the PCI. He was vice president of the Delegation for relations with Hungary. After that, he was on the Committee on Development and Cooperation, the Delegation for relations with the Member States of ASEAN and the ASEAN Inter-Parliamentary Organization (AIPO). In 1993, Trivelli became a part of the Delegation to the EC-Turkey Joint Parliamentary Committee. In 1994, Trivelli was elected to the Committee on Foreign Affairs and Security.[1]