In 1930, Hanoi artist Cát Tường, also known as Le Mur, designed a dress inspired by the áo ngũ thân and by Paris fashions. It reached to the floor and fit the curves of the body by using darts and a nipped-in waist.^[7] When fabric became inexpensive, the rationale multiple layers and thick flaps disappeared. Modern texile manufacture allowed for wider panels, eliminating the need to sew narrow panels together. The áo dài Le Mur, or "trendy" ao dai, created a sensation when model Nguyễn Thị Hậu wore it for a feature published by the newspaper Today in January 1935.^[8] The style was promoted by the artists of Tự Lực văn đoàn ("Self-Reliant Literary Group") as a national costume for the modern era.^[9] The painter Lê Phô introduced several popular styles of ao dai beginning in 1934. Such Westernized garments temporarily disappeared during World War II (1939–45).

This woman wears a white ao dai in front of Hồ Gươm Lake in Hanoi.

In the 1950s, Saigon designers tightened the fit of the ao dai to create the version commonly seen today.^[2] Trần Kim of Thiết Lập Tailors and Dũng of Dũng Tailors created a dress with raglan sleeves and a diagonal seam that runs from the collar to the underarm.^[2] The infamous Madame Nhu, first lady of South Vietnam, popularized a collarless version beginning in 1958. The ao dai was most popular from 1960 to 1975.^[10] A brightly colored áo dài hippy was introduced in 1968.^[11] The áo dài mini, a version designed for practical use and convenience, had slits that extended above the waist and panels that reached only to the knee.^[7]