Her maternal grandfather was composer Alfredo Casella. She moved to Rome in the late 1960s. In 1970 she participated in the television variety show Babau in four episodes, written by Poli Paul and Ida Omboni and directed by Vito Molinari.
Because of program content deemed outrageous at the time, the show was "archived" and only broadcast by Radiotelevisione Italiana six years later.
In the early 1970s Nicolodi had some significant work in the cinema and theater under the guidance of Elio Petri. Also in the same year, Nicolodi participated in some television productions, such as the serial story Nicotera, Without a Trace with Rossano Brazzi (1972), Portrait of a Veiled Woman with Nino Castelnuovo (1975), the drama Saturnino Farandola with Mariano Rigillo (1978), and Rosaura at 10 (1981).
Nicolodi starred in five films directed by Dario Argento between 1975 and 1987: Deep Red (1975), Inferno (1980), Tenebrae (1982), Phenomena (1985), and Opera (1987). She also has a co-writing cr on Suspiria (as well as an uncredited cameo role as "Woman at Airport").
Notably, Nicolodi starred in Shock, the final film of Italian horror auteur Mario Bava.
In 2012, Nicolodi was highlighted in the retrospective Argento: Il Cinema Nel Sangue at the Museum of Arts and Design in New York City. The retrospective celebrated the influence of the Argento family on filmmaking in Italy and around the world.