He previously served as mayor of his native Metković[2][3] from 2013 to 2016, and Deputy Prime Minister in the cabinet of Tihomir Orešković from January until his election as speaker in October 2016.

[3][6] He is married to Maša Petrov, a primary school teacher, with whom he has three sons: Jakov, Dominik, and Andrija.

Petrov began his political career as an independent candidate in the 2011 parliamentary election on the list of the conservative Croatian Growth (HRAST) party.

[7] On 17 November 2012, Petrov and other local politicians and activists life founded the Bridge of Independent Lists (MOST) as a regionalist political platform and was chosen as its first president.

[11] For the 2015 parliamentary election, Petrov's Most party went national and was joined by independent local politicians from other parts of the country.

The party had a crucial role in forming the new government and started negotiations with the ruling centre-left Croatia is Growing coalition, centred around the Social Democratic Party (SDP), and the opposition centre-right Patriotic Coalition, centred around the Croatian Democratic Union (HDZ).

[20] In February, the Most party prepared amendments for reducing benefits of members of the parliament, but the bill was stopped and did not reach voting in the Sabor.

[22] In the same month, Petrov started negotiations with labour union representatives over a 6 percent wage increase for public sector workers, as GDP grew over 2% for two consecutive quarters.

The government had not planned funds for the wage increase in the 2016 budget and wanted to negotiate new terms of the contract, as there was no money for its implementation.

[27] On 3 June, in an attempt at a compromise solution, Prime Minister Tihomir Orešković called on Petrov and Karamarko to resign for the sake of stability of the country.

Petrov responded that he is ready to step down if it will help stabilise the situation in the country,[28] while Karamarko refused to resign and stressed out that Orešković no longer has the support of HDZ.

As per a post-election agreement between Petrov's Bridge of Independent Lists party and the Croatian Democratic Union (HDZ) led by Prime Minister Andrej Plenković, Petrov was due to serve as speaker for a 2-year period and would thereafter have been replaced by speaker from the HDZ, presumably the party's general secretary and former foreign minister Gordan Jandroković.