Preus museum's collections are based on those of the former Preus fotomuseum, which was acquired by the Norwegian state in accordance with Royal Proposition 56 (1993-94) "Skiping av eit nasjonalt fotomuseum" (Establishment of a National Museum of Photography), a resolution passed by the Norwegian parliament on 27th May 1994.

The collections consist of photographs, albums and images of various other types, cameras and other technical equipment, and a specialist library. The picture collection is broadly representative of the history of photography as described by Beaumont Newhall and Helmut Gernsheim. Especially well represented in the collection are the early history of photography from the 19th century, pictorialism as it developed in English and German speaking countries and among Norwegian camera clubs, and new objectivism and modernism as these developed in the German speaking countries and in eastern Europe. The primary focus of the Norwegian material was originally on early landscapes and portraits, together with considerable material from the realm of fashion/advertising and art photography. Over the past ten years, the collection has been expanded with many works by Norwegian photographers active in the field of art photography, as well as by professionals and amateurs working with documentary, advertising and portraits. The collection is also strengthened by the purchase of pivotal works by international contemporary artists and Norwegian artists working in the expanded field of photography.

With its broad temporal and genre perspective, it goes without saying that the collection represents a significant number of processes that illustrate the historic development of photography: from daguerreotypes, autochromes and stereo photography through to contemporary colour photography, and from early photo-mechanical techniques through to modern digital printing. The museum's extensive collection of cameras and other technical equipment both supplements the technical aspects of the history of photographic processes and tells the story of a major international industry built on the determination to create pictures: from the 18th century camera obscura to the daguerreotype camera, special cameras for microscopic, panoramic, stereoscopic photography, cameras for espionage, three-colour pictures, portraits or travel; folding cameras and box cameras, single and dual lens reflex cameras, small image cameras and miniature cameras.

The book collection encompasses literature from the 16th century through to today. The history of photography is told here in all its complexity by means of various focal themes such as chemistry, optics, art, technology, as well as through user manuals and textbooks. The collection also contains a large number of books with original photographs and seminal works about countless photographers, in addition to an extensive collection of journals including major titles such as Camera Work, Camera Notes and Life. There is also a large number of Scandinavian and European photography journals for both amateurs and professionals. The book collection functions as a library.

The museum also has collections that explore specific aspects of photography or related themes in greater depth: early film equipment, the Mogens Skott-Hanssen collection (illusionism) and "The French Collection" (paintings and prints with motifs relating to photographers and photography).