Mandelli was born in Bergamo on January 31, 1925.[3][2] She had a talent as a seamstress and an interest in fashion, but studied to be a teacher based on her mother's advice.[2] Mandelli worked as a teacher for several years until her friend, Flora Dolci, offered use of a flat in Rome for six months rent-free.[1][2] She purchased an old sewing machine in the early 1950s and founded her label, Krizia, in 1954 by selling clothes from her Fiat 500.[2]
In 1964, she unveiled her first black-and-white collection at the Palazzo Pitti in Florence, which earned a Critica della Moda award.[1][2] The fashion house grew rapidly during the 1960s and 1970s. Under Mandelli, Krizia released a version of shorts cut "very short" in 1971, now seen as an early form of hot pants.[1] Krizia grew into a $500 million business at its height during the 1990s.[2]
By the end of the 1980s, she bought land in Punta Volpe, Costa Smeralda, and hired the architect Gianni Gamondi to build a luxurious seafront loggia. The property was listed on sale by Sotheby's in 2022.[4]
Mariuccia Mandelli died at her home in Milan on December 6, 2015, at the age of 90.[1][2]