Marjanović was born into a large working-class family with 7 children in Knin, in the Littoral Banovina of the Kingdom of Yugoslavia. He had 4 brothers and 2 sisters. His father, Dušan, worked in the local factory, while mother Marija was a homemaker. After completing primary school and gymnasium in his hometown, Marjanović moved to Zagreb where he attended musical academy which he never finished. He then moved to Belgrade, where in 1960 he graduated at University of Belgrade's Faculty of Economics, more specifically at the department for microeconomics. Upon graduation, Marjanović came back to Knin since he found employment there as the supervisor in Tvik factory. From there, he advanced to the position of financial director, and eventually moving on to metallurgical factory in Zenica. In 1973, he transferred to the Moscow outpost of Progres - a state company that handled close to 80% of Yugoslav black metallurgy and other heavy industries. By 1976 he quickly advanced up the ranks to become one of the directors at Progres. He handled company's steel division in Russia quite successfully while developing an impressive network of influential friends and business partners such as Viktor Chernomyrdin, and Yuri Brezhnev, son of Leonid Brezhnev. In 1979, Marjanović was named as Progres' general director. From 1989 until 1994, he was the president of FK Partizan's executive board. One of his more notable moves while at the post was bringing Predrag Mijatović to the club in December 1989. Mijatović, at the time a young promising player from Titograd's FK Budućnost, was very close to signing with Hajduk Split when Marjanović stepped in and convinced him to come to Belgrade. Upon leaving the club, Marjanović was named Partizan's honorary president.
Marjanović officially commenced his PM term on 18 March 1994. He was widely regarded as little more than a puppet of then Serbian presidentSlobodan Milošević.
Prime Minister of Serbia 1998-2000
After early parliamentary elections in late 1997, Milošević's SPS-led coalition formed a government with far-right Serbian Radical Party led by Vojislav Šešelj. Marjanović was picked for another PM term that started on March 24, 1998. Naturally, Marjanović continued as a mere extension of Slobodan Milošević who at this time held the post of President of Yugoslavia. Here's how sources from the top levels of Milošević's Socialist Party of Serbia described Marjanović's government modus operandi in Evropljanin magazine: Prime Minister Marjanović suggests something – ministers do not vote – and then Marjanović simply concludes the matter as agreed on. Of course Marjanović neither suggests nor concludes anything without first consulting Milošević. Even deputy PM Vojislav Šešelj indirectly confirmed this operating procedure when he said the government meetings are always well prepared, never lasting longer than 15–20 minutes. This two-year period is widely seen as the most brutal whilst Serbia was led by Milošević. Marjanović's government, passed two of what critics consider to be the most draconian pieces of legislation in Serbian political history: the University Law that stripped the University of Belgrade of its autonomy, opening the way for the government to install professors, deans and rectors, as well as the Information Law, which aimed to restrict the activities of media financed by political enemies; despite this, the media played a prominent role in the 5 October2000 coup d'état. Similarly to his first term in office, Marjanović again took a back seat, leaving the limelight to more aggressive members of his cabinet like deputy PM Šešelj and Minister of InformationAleksandar Vučić. On 21 October 2000, two weeks after the Bulldozer Revolution, Marjanović resigned to be replaced by a transitional governmentcomposed of the Democratic Opposition of Serbia, the Socialist Party of Serbia, and the Serbian Renewal Movement until new parliamentary elections could be organized.
Business career while in office
Marjanović continued to lead Progres all throughout his six and a half years as Serbian PM, though he claimed his status at the company was frozen. The company, which during the 1990s started importing gas from Russia was still officially publicly owned. Although allegations of wrongdoing ran rampant for years, Marjanović was never prosecuted. No legal action was taken against him after the new authorities took office following the overthrow of Slobodan Milošević in October 2000. On 23 January 2002, Marjanović was re-elected as Progres' main board president.
Death
He died on 21 February 2006, in Belgrade, at age of 68, from undisclosed causes.