After the war Aniasi left the PCI, adhering (after 1947) to the Italian Democratic Socialist Party (PSDI). Aniasi was a councilman of Milan from 1951 to 1967, when he became Mayor of the city following the resignation of Pietro Bucalossi; he contributed to Bucalossi's fall by leaving the PSDI to join the Italian Socialist Party (PSI).[2] Mayor during the "Years of Lead", Aniasi was often in disagreement with the prefectLibero Mazza: while the latter supported law and order policies against the Red Brigades and other terrorists, Aniasi supported disarming the police instead. Aniasi was also criticized for seemingly downplaying terrorism.
After 1994, he left politics temporarily before joining the Democrats of the Left (DS), becoming a member of its directive council. He died in Milan in 2005 and is buried at the city's Monumental Cemetery.[3]