[5] His father was Ernest Krauss, a Hungarian by birth, who had gone to Trieste as a young man and married wealthy heiress Bianca Castelli,[6] from an established family of coffee importers.

[4] After earning a law degree at the University of Milan in 1924, Castelli returned to Trieste, where his father had secured a job for him with an insurance company.

There, Ileana's taste and money helped him start his first gallery at Place Vendôme in Paris, which was named for its co-director, the decorator René Drouin,[5] and situated between the Ritz Hotel and the couturier Elsa Schiaparelli.

[9] Specializing in surrealistic art,[6] the gallery opened in July 1939, with a show of modern and antique furniture, including commissioned pieces by Drouin, Max Ernst, Meret Oppenheim, Leonor Fini (a former girlfriend of Castelli's from Trieste), Eugene Berman, and other artists in the force field of Surrealism.

Castelli's parents did not escape but died in Budapest, hounded by members of Hungary's fascist Arrow Cross Party.

[5] In New York, the Castellis were two of only three non-artist members (the other was dealer Charles Egan)[5] of the Club, an influential coterie founded in 1949 that included Willem de Kooning, Robert Rauschenberg, Franz Kline, and Ad Reinhardt.

Jackson Pollock, Willem de Kooning, Cy Twombly, Friedel Dzubas, and Norman Bluhm were some artists who were included in group shows.

From the early 1960s through the late 70s, Frank Stella, Larry Poons, Lee Bontecou, James Rosenquist, Roy Lichtenstein, Andy Warhol, Robert Morris, Donald Judd, Dan Flavin, Cy Twombly, Ronald Davis, Ed Ruscha, Salvatore Scarpitta, Richard Serra, Bruce Nauman, Lawrence Weiner and Joseph Kosuth joined the stable of Castelli artists.

When Castelli discovered Serra in 1967, for example, he offered him a guarantee of three years of monthly payments even though he did not expect to sell any of the unknown sculptor's lead-plate work in that time.

In 2015, Bertozzi Castelli opened a one-room satellite gallery at 1046 Madison Avenue, near 80th Street, with Robert Morris's installation Lead and Felt (1969).

[15] Castelli received the rosette of the French Legion of Honor, allegedly in exchange for donating works by Johns to the Centre Pompidou.

Frank Stella named a work after him, in 1992 he posed for the French artist Klaus Guingand who immortalized his shadow, and a sculpture by Robert Morris, Leo, places a brain at the center of a target.

In 1992, amid rumors that Castelli was negotiating to sell his archives to the Getty Center in Los Angeles, his collection was said to be worth some $2 million.