Although he was a qualified architect, the rise of the National Socialists meant that Andreas Feininger was unable to find work in Germany, nor in Paris after his emigration there, and lost his work permit in Sweden. In New York he turned to photographing architecture and started a lifelong career as a photographer exploring the city's streets, working as a photojournalist and photo theorist and writing a large number of photography manuals.

His interest in photography can be dated to the 1920s, when Andreas Feininger, son of the American-German painter Lyonel (1871–1956) and Julia (born Lilienfeld, 1880–1970) Feininger, studied carpentry at the Bauhaus in Weimar, then later, between 1925 and 1928, architecture at the Staatliche Bauschule Weimar. In Dessau he created his first darkroom in the cellar of the family home where his brother T. Lux Feininger also lived. Andreas Feininger’s first job as an architect was in Hamburg, where he also spent time photographing the city. (These images were first published in the photobook Feininger’s Hamburg in 1980.) In Hamburg he also met the photographer Herbert List, who was a friend of the photographer Rolf Tietgens. Feininger continued to practise architecture until 1931, but being French-born and half Jewish he was forced to leave Germany in 1932 and went to Paris to join his brother Lux Feininger, who had also studied at the Bauhaus and was pursuing a career as a painter and photographer. In Paris, Andreas Feininger obtained a job with the French architect Le Corbusier, but his salary was never paid. As in Hamburg, he discovered the city through photography on his walks. Finally he emigrated in 1933 to Stockholm, where he joined his student friend and later wife, Swedish-born Getrud Wysse Hägg (1912–2006). Wysse Hägg had trained at an arts and crafts school in Stockholm and, during the 1920s, had also studied graphic design at the Bauhaus in Germany, where she had first met Andreas Feininger. In Stockholm, she designed decor for the Swedish Gustavsberg porcelain factory, where her uncle Wilhelm Kåge was artistic director.

In Stockholm Andreas Feininger tried to restart his architectural practice but soon began working as a professional photographer and receiving commissions. Besides architecture and industrial objects, he was also interested in the forms of nature and made technical experiments, making his own telephoto lens in 1934. With this lens, a new discovery of the city began. As the inequalities and different proportions between the architecture, the city and the human scale were less than with a normal camera lens, Andreas Feininger was able to capture the people and their surroundings in an equal perspective, which was much truer to reality, offering a new visual experience. After the outbreak of World War II, Feininger, as a foreigner, lost his work permit in Sweden. At the end of 1939, the family (Andreas and Wysse had married in 1933 and in 1935 their son Tom was born) decided to emigrate to New York, where his brother Lux Feininger had lived since 1936 and his parents Julia and Lyonel Feininger since 1937. As Lyonel Feininger had been born in New York, Andreas Feininger was half American and already had American citizenship before arriving in the metropolis, but as his mother was Jewish he was afraid of persecution.  

The family initially lived in New York at the Hotel Earle in Washington Square and in 1940 moved to an apartment with a view of the Hudson River, at 365 West 20th Street, where they lived until the 1980s. During their early days there, Feininger photographed the apartment and the rooms he had transformed into a studio and darkroom. In January 1940 he began working for the Black Star photo agency, where many other émigré photographers had found work after their arrival (Walter Sanders, Fred Stein, Lilly Joss Reich, Fritz Henle, Carola Gregor, Ilse Bing, Werner Wolff, Ruth Bernhard). Andreas Feininger probably knew at least one of the three Black Star founders, Kurt Safranski, Kurt Kornfeld and Ernest Mayer, from his Berlin days and so was able to make contact with them in New York. As Andreas Feininger recounted in his autobiography In Retrospect (1988), the early days in New York were not easy. First, they had to learn a new language, he was the only member of the family in work and was not well paid by the photo agencies. In addition, most of his German photographic equipment was not compatible with the American system. Throughout his career as a photographer he was always on the lookout for new camera equipment and lenses and was very interested in unusual types, which he mostly found in second hand camera shops. One of these finds was a telephoto and wideangle lens, which he used for many of his New York images. Depending on subject and genre, he used different cameras, with or without a tripod.  

In January 1941 Andreas Feininger’s contract with Black Star ended and, feeling exploited and underpaid, in 1942 he started to work as a retainer photographer, becoming in the same year a staff photographer at Life magazine, where he worked until his retirement in 1962. During these years he got more than 340 assignments and his images were printed in many different magazines and newspapers around the world. During the 1940s, with the help of his photojournalism network, he also published some of his photographs of Stockholm in Swedish newspapers and magazines.

For commissions as well as in private sessions, Andreas Feininger soon began exploring New York City with his camera and started his photographic cartography of the metropolis. Fascinated by the contrasts of the city, the iron structures of the elevated railways and fire escapes, as well as the cultural diversity on the streets, he created his experimental views of New York. Besides the architecture, he was also interested in the graphical language and urban patterns of the city, as well as in its history, and collected old maps and prints. He meticulously marked on each of his contact sheets the exact address where the image was taken. During this time he developed a photographic knowledge of the city, photographing at different times of day and learning the perfect light conditions and best viewpoints in Manhattan. As well as photographing the inner city, he also tried to capture views of the city and its skyline, which he discovered from a distance. After a year in New York, the family could afford to buy a car and, while their son Tom was at school, Wysse and Andreas Feininger travelled out of Manhattan to New Jersey, where he took his first views of the city with a tele lens. Besides assisting her husband and acting as a model in some of his photos, Wysse Feininger began a career as a commercial artist and illustrator of children's books and, less frequently, as a clothing designer. However, from 1943, she mainly assisted her husband with his several hundred photo reportages, mainly for Life magazine. After Andreas Feininger's death, she curated exhibitions and administered his estate.

In the April 1941 issue of Life, under the title “New York. A Big spectacle in big pictures” nine pages were devoted to a photographic essay featuring Andreas Feininger’s urban views (Life, 14 April 1941, pp. 86–95). The cover photo was by another émigré Life staff photographer, Walter Sanders, showing an unsual view with the American flag flying on a ship heading towards the Manhattan skyline. In 1945 Andreas Feininger published his New York images in the photobook New York (Ziff–Davis). He was well embedded in the New York photographic scene and a number of émigré colleagues, who probably knew him from Germany, made portraits of him. These included Fritz Neugass, Fritz Henle and Hermann Landshoff.

It is known that he often used the Leco photofinishing service, founded by the émigré Leo Cohn and an important contact hub for photographers and editors, who would catch up on the latest news  while waiting for their prints to be developed. Besides his street and city images and commissioned work, Andreas Feininger also pursued a photographic interest in the phenomena of nature in his series and studies of plants and shells – a similar approach to that of émigré photographer Ruth Bernhard. During World War II, Andreas Feininger worked at the Office of War Information and was responsible for the photographic documentation of American war industries on the home front. As can be seen in his archived maps and folders and the travel souvenirs in his scrapbooks, the month-long trips took him all over the U.S and were mostly made by train since petrol was rationed during the war.

From the 1930s Andreas Feininger also published technical texts and practical guides on photography. He had played a similar educational role during his exile in Stockholm. From the mid-1940s, besides in such magazines as Minicam, The Complete Photographer and U.S. Camera. His guides and text also appeared in Popular Photography. With the help of his own images, he mainly explained certain practical and technical photographic topics and problems. Between May and December 1949 he ran a serial feature dubbed “Feiniger’s Workshop” in Popular Photography, which appeared monthly and covered a number of themes: “Feininger’s Workshop- photo facts in pictures. Unsharpness and its cause” (May 1949) “Feininger’s Workshop – photo facts in pictures. The facts of about perspective” (June 1949) “Feininger’s Workshop – photo facts in pictures. Imaginative Print Control” (July 1949); “Feininger’s Workshop – photo facts in pictures. Controlling Those Verticals” (August 1949); “Feininger’s Workshop – photo facts in pictures. Texture Rendering with Light” (September 1949); “Feininger’s Workshop – photo facts in pictures. Halation, Flare and Stars” (October 1949); “Feininger’s Workshop – Testing Your Lens for Defects” (December 1949). Popular Photography was an important magazine for émigré photographers, who were able to publish both their images from their previous times in Europe as well as newer photographs from their exile in New York. Among the émigré photographers published were Lucien Aigner, Ruth Bernhard, Erwin Blumenfeld, Josef Breitenbach, Alexey Brodovitch, Rudy Burckhardt, Alfred Eisenstaedt, Philippe Halsman, Fritz Henle, Ruth Jacobi, Lilly Joss, Clemens Kalischer, George Karger, André Kértész, Hermann Landshoff, Lisa Larsen, Herbert Matter, Hansel Mieth, Lisette Model, Martin Munkacsi, Fritz Neugass, Walter Sanders, Kurt Safranski, Xanti Schawinsky, Rolf Tietgens, Werner Wolff, Roman Vishniac and Ylla.

Besides his work for Popular Photography, Andreas Feininger also published more than 40 books, up until the 1980s. These included photographic handbooks as well as photobooks. His first book in the US as author was New Paths in Photography (American Photographic Publishing, 1939), followed by Feininger on Photography (Ziff-Davis, 1949), Advanced Photography (Prentice-Hall, 1952) and The Face of New York (Crown, 1954). Through his contact with Walter Heering, Andreas Feininger already had experience of writing about photography in Germany. From 1933 he wrote for Walter Heering’s magazine Foto-Beobachter and in 1934 published his first book Menschen vor der Kamera, on portrait photography. Although he had emigrated to Stockholm at the time, in 1936 and 1937, four books of his were published by the Heering Verlag publishing house with the help of Walter Heering:
Vergrößern leicht gemacht, Motive im Gegenlicht, Selbst entwickeln und kopieren, Aufnahmetechnik, Fotografische Gestaltung (Walter Heering Verlag, 1937). Last but not least, in 1936 a photobook of his Stockholm images also appeared. A few books of these books were translated into English after his arrival in New York, among them Exakta. Ein Weg zu Foto-Neuland (Gerhard Isert Verlag, 1939) which appeared in its English edition New Paths in Photography (American Photographic Publishing, 1939).

Despite his successful career as a photographer and the immense volume of published images and written works, Andreas Feininger had his first group show with In And out of Focus in 1948 at the Museum of Modern Art, with another, The Anatomy of Nature, at the American Museum of Natural History in 1957. Other émigré photographers who were represented at the exhibition In and Out of Focus were Josef Breitenbach, Marion Palfi, Fritz Goro (the husband of Carola Gregor), Lotte Jacobi, Lisette Model and Ylla.