Niclas Hammarström was born in Sweden in 1969. When he was 14, he started to take pictures at the Solvalla horserace track. He later studied photography in Stockholm. After his studies, he worked at various newspapers in Sweden. In 1993, he began working as a contract photographer for the Swedish daily Aftonbladet, as their US-based photographer. While living in New York City, Hammarström photographing events in the US, Canada, and South America for almost five years. He covered major events, such as the siege in Waco, the World Trade Center bombing, the Oklahoma City bombing, the 1994 soccer World Cup, and the 1996 Olympics in Atlanta, as well as numerous Mike Tyson fights in Las Vegas.
In 1997, he returned to Sweden and joined the Aftonbladet staff, covering primarily sports for the next five years. In 2002, after the Olympics in Salt Lake City, he left Aftonbladet, stopped working as a photographer and joined the family business selling and manufacturing handicap aid tools. In 2010, he sold the company and stayed home taking care of his family for a year, before realizing that he wanted to return to photography. In March 2011, he returned to Aftonbladet as a freelance photographer for the newspaper.