Born in Bologna, Emilia-Romagna, Baldi graduated in Social science at the Sapienza University in Rome and then enrolled at the Centro Sperimentale di Cinematografia. He debuted as a director of documentary shorts, and in 1958 he won the Golden Lion for best short film at the Venice Film Festival with "Il pianto delle zitelle" ("The crying of spinsters"). He directed a number of independent films, generally characterized by social criticism. His film "Fuoco!" entered the main competition at the 29th Venice International Film Festival, while the film "L'ultimo giorno di scuola prima delle vacanze di Natale" (aka "The Last Day of School Before Christmas") was screened at the 1975 Cannes Film Festival in the Directors' Fortnight section.