Visart, born in 1909, was sent to Hollywood School for Girls in 1920 where she became great friends with Katherine DeMille, adopted daughter of Cecil B. DeMille, and subsequently spent a lot of time with the DeMille family who were apparently very fond of her. In 1929, Visart met designer Mitchell Leisen who was working for DeMille at this point and they became romantically involved. Visart became Leisen's protégée working behind the scenes at Paramount studios with her mentor Leisen some time before she was credited for doing so. It appears that Leisen groomed her to take his place as he started to direct his own films and began to extract himself from DeMille's unit.
In 1932, Leisen was frantically busy with the production of The Sign of the Cross designing costumes and sets with Travis Banton and acting as assistant director. During this production, Leisen apparently asked Visart to design a number of costumes under his and Banton's supervision.
After Sign of the Cross Visart collaborated with Banton again for DeMille on Cleopatra, 1934 and The Crusades, 1935, although accounts of her career rarely credit her involvement with these three important titles. In 1936 at the age of twenty-seven Natalie Visart was appointed Head Costume Designer for Cecil B. DeMille.