Igor Grosu holds a license in history and worked for years as an expert for various projects.

He earned the position of deputy minister of education at the time when Maia Sandu was the head of the Education Ministry. In August 2015 Prime Minister Valeriu Strelet relieved Mr. Grosu from office “upon personal request” and appointed him as his senior state advisor on education, sciences, healthcare and social protection. There he resisted several months until Interim Prime Minister Gheorghe Brega dismissed him.

Mr. Grosu followed his former ministerial boss Maia Sandu to found the Action and Solidarity Party (PAS). He was elected as the general secretary of the newly-formed political party.

At the parliamentary elections in February 2019, Mr. Grosu ran on behalf of ACUM (PAS+DA) in the uninominal constituency №20 Straseni, where he lost to Democrat Pavel Filip, the acting premier during that period. Nonetheless, Mr. Grosu entered the Parliament on the ACUM national list where he was the fourth candidate.

After Maia Sandu became the leader of the country, following the presidential elections of 2020, thus, being forced to resign from the position of PAS president, Igor Grosu took over the acting position. He had previously been PAS's first deputy president.

On 16 March 2021, after rounds of consultations with parliamentary factions, as well as Mariana Durlesteanu's decision to withdraw her candidacy for prime minister, a position she had been promoted by a majority coalition of the Socialist Party, Shor Party, "Pro Moldova" platform and several independent MPs, President Maia Sandu appointed Igor Grosu’s candidacy for prime minister. However, early parliamentary elections were later initiated. At the polls, Grosu opened the PAS list and entered the Parliament. He was elected President of the Legislature.

Igor Grosu is one of the founders of several notorious nonprofits in Moldova: Amnesty International Moldova; “Contact” NGO National Information Center; Pro-Democrație Association; National Youth Council of Moldova; and Center for Reform Analysis and Assessment.