During his parliamentary career, Jandroković, among other functions, served as the chairman of the Committee on the Economy, Development and Renovation from 2003 to 2004, and as the chairman of the Foreign Policy Committee from 2004 to 2007. In the same period he served as the chairman of the Delegation to the Croatia – EU Joint Parliamentary Committee. In the 7th term of the Croatian Parliament, from 2011 to 2015, Jandroković was the deputy chairman firstly of the European Integration Committee and then of the European Affairs Committee, founded upon Croatia's entry into the European Union. He was elected the chairman of the European Affairs Committee on 23 January 2016. Following the extraordinary parliamentary elections in September 2016, he was elected the Deputy Speaker of the Croatian Parliament on 14 October 2016.
As per a post-election agreement, set up in 2016, between the two parties in the governing coalition: the Croatian Democratic Union (HDZ; led by Prime Minister Andrej Plenković) and the Bridge of Independent Lists (Most; led by Božo Petrov, who would later be elected speaker of Parliament), Jandroković was supposed assume the speakership some time in 2018 (the middle of the current legislative term, due to end in 2020). However, due to the breakup of the coalition between the HDZ and the Most, Božo Petrov resigned as speaker on 4 May 2017, while Jandroković was voted into office as the new speaker the day later.[2] Jandroković was re-elected as speaker on 22 July 2020 following the 2020 election.[3]