With a diploma in law, Serghei Sirbu had worked in the presidential administration at the time when Communists Party (PCRM) leader Vladimir Voronin was in charge there. In late 2012 he left PCRM – which gave him a seat in Parliament – and half a year later he joined the faction of the Moldovan Democratic Party (PDM).

He was one of the most active members of the PDM faction, with a record of bills proposed for adoption.

The February 2019 elections helped Mr. Sirbu remain in Parliament on PDM’s national candidate list.