An authentic aristocrat, born in Paris to a family claiming ancestry that dates back to the First Crusade. His grandfather was a Russian Ambassador, his mother an Italian Countess. Cassini studied in Florence, apprenticed for Patou in Paris, then opened his own boutique in Rome. The fascist regime in Italy in the 30's drove Cassini and his family to America. Renouncing his title of Count, he became a US Citizen in 1942. After a brief attempt at costume design for Broadway plays, Cassini headed for the glamour of Hollywood. He worked for all the major film studios in the 40's, dressed countless movie stars and married Gene Tierney (star of Laura). Cassini was also engaged to Grace Kelly who later married Prince Rainier of Monaco. After serving in the US Calvary Corps during World War II, he returned to New York to open his own fashion house on Seventh Avenue. His reputation developed as a result of his genius for original spontaneous design.

Fashion historians credit Cassini with numerous design accomplishments including the sheath, the A-Line, the little white collar dress, the knit and the military look for women. With his designs for Jacqueline Kennedy, he achieved international acclaim and brought world wide attention to American fashion. Next, he tackled menswear, breaking tradition with innovations impossible to ignore. Cassini revitalized men's fashion by bringing color to shirts that had only been white. By putting his name and his magic touch on everything from fashion to fragrance, carpets to greeting cards, Cassini has given millions of Americans a little bit of aristocracy to call their own.

Cassini passed away in March 2006 at the age of 92. He leaves behind his beloved wife Marianne, who currently runs the Oleg Cassini business, as well as two daughters, Antoinette and Christina (mother is first wife Gene Tierney)