She made her stage début at the Bergen theatre Den Nationale Scene in 1899, and joined Sekondteatret in its first season, until she got married.

She participated in Danish films in the mid-1910s, appeared regularly at Centralteatret from 1916 to 1921, and had a three years assignment as actress for Det Nye Teater from 1928.

[1] Her eldest brother Johan Ernst was a merchant and leading politician in Bergen, and served in the Norwegian Parliament for one period.

[2][3] Johan Ernst supported her morally when she chose to embark on a theatrical career, and later helped her financially when needed; he funded her visits to England and Paris.

[4] She was a second cousin of Prime Minister Johan Ludwig Mowinckel, and a sister-in-law of the theatre critics Gunnar Heiberg and Sigurd Bødtker.

[11] Back in Bergen she worked as a teacher at a girls' school; she also took lessons with instructor Ludovica Levy at Den Nationale Scene.

[1] She made her stage début at Den Nationale Scene on 2 January 1899, as "Anna Hielm" in Heiberg's play Kong Midas.

[1] She was offered a position at Den Nationale Scene in Bergen, but chose to join Ludovica Levy at her Sekondteater in Kristiania.

[15] Her first appearance at Nationaltheatret was in 1902, in a few performances when she replaced Ragna Wettergreen in the title role in Ibsen's Fru Inger til Østeraad.

Finding herself in a situation with no place to live, no money and no job, and with three small children, Mowinckel joined the touring theatre Nationalturneen for the 1909/1910 season, as an actress and also as responsible for the costumes.

[23] In London she fell under the spell of Gordon Craig, admiring his theories on theatrical design, such as stage composition and use of light.

Among the visitors were theatre critic Sigurd Bødtker, who eventually moved in with her, Olaf Bull, Nils Kjær, Helge Krog, Ronald Fangen, Sigurd Hoel, Nini Roll Anker, Oda Krohg, Hulda Garborg, Sigrid Undset, Jens Thiis and Sven Elvestad.

[34] In 1921, her performance of the title character in Ibsen's Fru Inger til Østeraad at Centralteatret was a popular success, garnering praise in critical reviews.

[37] In a retrospective article from 1939 Anton Rønneberg characterized this event as an important day in the history of Norwegian theatre.

[40] Her first production was Myrkemakti (Russian: Власть тьмы) by Tolstoi in February 1923, after which she was appointed as stage instructor for Det Norske Teatret for a period of two years.

In March of the same year she produced Rytter's Herman Ravn, in April Ørjasæter's début play Jo Gjende, and in October Čapek's R.U.R..

[43] In 1924 Mowinckel staged Crommelynck's play Den praktfulde hanrei (in French: Le cocu magnifique) at Det Frie Teater.

[47] Her first production was a success, an adaptation of Vane's play Outward Bound (translated as Norwegian: Til ukjent havn), staged in September 1925.

[63] At Det Norske Teatret in March 1931 she staged an adaptation of Frank's Carl and Anna, in October O'Neill's Alle Guds born har vengjer, and in November 1931 Soini's Syndebukken.

In May 1932 she produced Martinez Sierra's play Dei spanske nonnone (Spanish: Canción de Cuna), in September Langer's Kamelen gjennom nålauga (Czech: Velbloub uchem jehly, in English: The Camel through the Needle's Eye), and in October 1932 Drabløs' adaptation of Falkberget's Eli Sjursdotter.

[64] In 1933 she staged Gjesdahl's adaptation of Winsloe's play Gestern und heute at Det Nye Teater, a performance which made a strong impression on the public.

Among her productions are Ibsen's John Gabriel Borkman and Rosmersholm, Bjørnson's Paul Lange og Tora Parsberg, Skram's Agnete, and plays by Pirandello, Borgen, Grieg and Abell[66] In April 1935 she produced Gorky's Jegor Bulytsjov at Det Norske Teatret, the first staged production of this play outside the Soviet Union,[67] and in October 1935 she produced Hoprekstad's historical comedy Jarlen.

[73] In January 1942 she produced Wessel's Kiærlighed uden strømper and in February Wiers-Jenssen's Anne Pedersdotter for Trøndelag Teater.

[74] In October 1942 she staged Kinck's play Agilulf den vise at the Det Norske Teatret, the last production before theatre director Hergel fled the country to escape the German occupation.

[75] In 1945 Mowinckel helped Jens Bolling with preparations for Studioteatret's first production, an adaptation of Wilder's play The Long Christmas Dinner, but she did not want to be credited.

[77] In October 1945 she produced Ibsen's Fru Inger til Østeraad for Trøndelag Teater, the theatre's first production after the occupation of Norway by Nazi Germany.

[79] During the summer 1946 the theatre toured Northern Troms and Finnmark, which had been severely damaged during the war, and they played Our Town at 26 different sites.

[81][82] She played the character "Bernanda" in an adaptation of Lorca's La casa de Bernarda Alba in 1947, staged by Gerda Ring.

[1] In May 1953 she staged Schiller's Maria Stuart at Nationaltheatret, at a gala performance for the official visit by Queen Juliana of the Netherlands.

Henrik Sørensen's painting is at Den Nationale Scene in Bergen, and a portrait by Kai Fjell is located at Nationaltheatret.