Bernardić was born in Zagreb on 5 January 1980 to civil servant, Damir Bernardić, and nurse, Dragica. His paternal grandfather's brother, Ivan Bernardić, was a notable member of the Croatian Peasant Party who was sentenced to long-term prison sentences in the Kingdom of Yugoslavia, the so-called Independent State of Croatia and the SFR Yugoslavia because of his political activism. His grandfather, Josip, was also prosecuted by the communists so he had to emigrate to Austria, where he died. His maternal grandparents were members of the Yugoslav Partisans. Having grown up in modest circumstances and wanting to help his parents financially by learning vocation, after finishing elementary school he enrolled in the First Technical School Tesla. He showed interest in mathematics and physics and in 1996 he become national champion in physics and competed for International Physics Olympics. At the national competition in 1997 he came in second, and in 1998 national championship first. He started working at age of 14. His father was participant of the Croatian War of Independence, and died in 1998. After finishing high school, Bernardić enrolled in the Zagreb Faculty of Science and since he was one of the best students he got a Nacional weekly scholarship which was handed to him by Prime Minister Ivica Račan. He was proclaimed a top student during his studies. In 2009, he became a research fellow at the postgraduate doctoral studies of physics at the Zagreb Faculty of Science. He also reported doctoral thesis in the Senate of the University of Zagreb, at the Zagreb Faculty of Economics and Business, on the topic of economics education with specialization in urban economics.
Political career
After becoming involved in politics in 1998 by joining the Social Democratic Party at age of 18, Bernardić was at first sticking posters, handing out leaflets and writing graffiti during party campaigns. He was actively involved in the SDP's Zagreb branch by having served as President of the Youth Forum branch, member of the Executive Board and member of the Zagreb Assembly. From 2008 to 2010, Bernardić served as leader of the SDP Youth Forum, and from 2008 to 2012 as member of the SDP's main board. On 5 May 2010, Bernardić defeated Ivo Jelušić, winning 63.3 per cent of the votes of those SDP members who cast their votes, and had become leader of the SDP's Zagreb branch. He also served as president of the SDP's Councilor Club in the Zagreb Assembly. On 20 October 2013, he was re-elected as head of SDP's Zagreb branch. Bernardić got involved in national politics in 2008 when he became MP by replacing Milan Bandić who was at the time still the SDP member. He was re-elected to the Parliament in the 2011, 2015, and 2016 parliamentary elections.
Personal life
Bernardić married an economist Irena Coljak on 29 April 2011, but it was revealed in October 2019, the couple got divorced. During high school, he played basketball, judo, karate and kung-fu. He speaks English fluently, and is learning French. Bernardić is a Roman Catholic who believes that the faith is a personal matter, and that everyone should be free to express it in, according to themselves, the most appropriate manner, adding that social democrats should stand for solidarity, human dignity and equality "which are the values on which Christian doctrine is based." He pilgrimages to Marija Bistrica.