Maurer was born in Bucharest to an Alsatian father of German descent and a Romanian mother, he completed studies in Law and became an attorney, defending in court members of the illegal leftist and Anti-fascist movements. Occasionally, as in the 1936 Craiova Trial of Romanian Communist Party (PCR) activists, including Ana Pauker, Alexandru Drăghici, and Alexandru Moghioroș, he assisted Lucrețiu Pătrășcanu).
Before 1937, he was briefly active in the Radical Peasants' Party, formed by Grigore Iunian as a splinter group of the National Peasants' Party; however, he was by then already a member of the illegal Communist Party and active in the Agitprop section.
In 1942-1943, during World War II he was imprisoned for his political activity (notably, in the camp at Târgu Jiu), and, as a member of a paramilitary grouping, played a secondary part in the events of 23 August 1944 that led to the downfall of the Ion Antonescu regime. During this time, although present among the few active leaders of the Party around general secretary Ștefan Foriș, he became a supporter of Gheorghe Gheorghiu-Dej's faction (dominated by imprisoned activists). In 1944, he played a hand in Foriș's deposition, assisting Emil Bodnăraș and Gheorghiu-Dej.
After the war, Maurer became a member of the Central Committee of the Romanian Workers' Party (the new name of the PCR after it had incorporated the Social Democratic Party) and took several ministerial positions in the new communist government of Romania — including that of undersecretary of the Communications and Public Works Ministry under Gheorghiu-Dej in the first Petru Groza government. In 1946-1947, he was a member of Romania's delegation to the Paris Peace Conference (headed by Gheorghe Tătărescu) and was briefly employed by Ana Pauker at the Foreign Ministry, before being dismissed for having an unsatisfactory level of political conviction. He was removed from the forefront for the following decade, working for the Institute of Juridical Research.
He supported Gheorghiu-Dej's nationalist policy, eventually becoming foreign minister of Romania in 1957 (replacing Grigore Preoteasa), holding office for six months, and serving in the delegations establishing closer contacts with the People's Republic of China during the Sino-Soviet Split and a détente with France in 1959.
Regarded, according to some claims, as Gheorghiu-Dej's chosen successor, he was head of state (President of the Presidium of the Great National Assembly of Romania) from 1958 to 1961. He took the seat previously occupied by Constantin Pîrvulescu on the Politburo, and then replaced Chivu Stoica as Prime Minister of Romania in 1961. In the latter capacity, he was the recipient of a 1963 letter by the British philosopher and activist Bertrand Russell, who pleaded with the Romanian authorities to free from jail Belu Zilber (a victim of the conflict between the Party leadership and Pătrășcanu, Zilber had been a political prisoner for sixteen years by then). Ion Gheorghe Maurer was also one of three acting Chairmen of the Presidium of the Great National Assembly (heads of state) between March 19 and March 24, 1965.
Alongside Emil Bodnăraș, Maurer was an important member of the Politburo in opposing the ambitions of Gheorghe Apostol and, together with Bodnăraș, helping along the establishment of the Nicolae Ceaușescu regime. Among others, Maurer helped silence potential opposition from inside the Party by withdrawing his support for Corneliu Mănescu and welcoming Ceaușescu's directives, before being himself criticized and sidelined (at the same time as his collaborator Alexandru Bârlădeanu). Pensioned in 1974, he was still present in the forefront at most Party ceremonies.
A prominent member of the nomenklatura for much of his life, he was known for his latent conflict with a large part of the PCR hierarchy. He accumulated a sizable wealth and was known for his ostentatious lifestyle. In 1989, Maurer's earlier support for Ceaușescu led the sidelined PCR members who were planning to state their opposition to the regime by drafting the so-called Letter of the Six (Gheorghe Apostol, Alexandru Bârlădeanu, Silviu Brucan, Constantin Pîrvulescu, and Grigore Răceanu) not to enlist his assistance in the process.
He died in Bucharest a decade after the Romanian Revolution, leaving a son, Jean.