Marlow studied psychology at Manchester University, graduating in 1974. He then started his career as an international photojournalist, working on an Italian cruise liner in the Caribbeanin 1975 before joining the Sygma news agency in Paris in 1976. In the late 1970s he worked in Northern Ireland and Lebanon, but soon found that the competition of photojournalism did not suit him. He returned home to Britain, and worked in Liverpool on an 8-year project. He became associated with Magnum photos in 1981 and became a full member in 1986.
In 1991 he received an assignment from the Somme department in France to photograph Amiens for which he turned to a slower medium-format, square-frame camera. Later he began to work abroad again, traveling to Japan, the United States, and other parts of Europe. His photography now is primarily in color. Though well known for his depictions of places, Marlow has also documented politics with a collaboration with Tony Blair.