Aart Klein’s career as a photographer began in 1930 with the photo press agency Polygoon. Although he was working there initially as an office clerk, he also started doing some photography himself. During his nine years at Polygoon’s, Aart Klein grew into one of the agency’s foremost photographers. Unfortunately, the negatives of the photographs he made in that period have been lost. During the German occupation, Aart Klein held a number of small jobs as a photographer. In 1943, he was forced to do labour in Germany, where he continued working as a photographer. After a year, he obtained leave, and when he got back to the Netherlands he went into hiding. During the last year of the German occupation, Aart Klein worked for the resistance and his photographs were passed on to England.

After Holland’s liberation in 1945, he set up the photographers' cooperative agency Particam with Maria Austria, Henk Jonker and Wim Zilver Rupe . The agency specialized in ballet, theatre and cabaret, and owed its monopoly in the field partly to the method Aart Klein and Maria Austria had developed to increase the sensitivity of slow films, so that there was no more need to use a flash during performances.

In 1956, Aart Klein left Particam and set up as freelance photographer. From that time on, he worked regularly for the quality paper Algemeen Handelsblad and was commissioned to produce a great number of photography books.

Infrastructure, urbanization, water and landscape are the thread that runs through Aart Klein’s whole oeuvre. In 1999, he explained the fascination these subjects held for him: 'I really grew up with the idea of ‘the Netherlands rising’. Industry, the Delta Works and ports are subjects that strongly appeal to me.' In contrast to many other photographers of his generation, people play a minor part in Aart Klein’s work and he developed his own vision on landscape photography.

He once said: ‘My photography is called black-and-white photography, but in fact it is just the other way round: white on black. Because if you don’t do anything, you get a black image. It’s only when you open the shutter that something happens: then you draw in white.’ The strong black-white contrasts originate from the period when Aart Klein participated in the cooperative photographer’s agency. Together with Maria Austria he devised a method of taking photographs in a theatre without having to use a flash. The negatives were ‘pushed’ in a well heated developer to achieve strong black-and-white contrasts. A major part of the artistic process took place while printing the negatives. In the dark room, Aart Klein determined quite precisely how he wished an image to be cropped.

The way he worked was often characterized as graphic; he thought this to be 'a rather superficial characterization that ignored the content'. Just as many other socially committed photographers, Aart Klein was a member of the photography branch of the Gebonden Kunsten federatie GKf (Bound Arts Federation) and was a co-founder of the Nederlandse Vereniging van Fotojournalisten (Dutch Association of Press Photographers). Although his work has been associated with ‘subjective photography’, that trend is more a confirmation of what he was already doing than a source of inspiration. He never joined the more aesthetically oriented Nederlandse Fotografen Kunstkring (Dutch Photographers Art Society).

In 1986, the Museum for Modern Art De Beyerd in Breda organized a retrospective. On that occasion, a boxed set containing two portfolios with unknown work by Aart Klein made its appearance. In 1982, Aart Klein received the Capi-Lux Alblas Prize and in 1996, the Fonds voor Beeldende Kunsten, Vormgeving en Bouwkunst (Foundation for the Visual Arts, Design and Architecture) awarded him the photography prize for his entire oeuvre.