John Ericson was born in Düsseldorf, Germany to a German chemist father and a Swedish actress and opera singer mother. When he was just three years old, his family fled the Nazi regime and emigrated to the United States, initially settling in Detroit before moving to New York.
Ericson's early life was marked by a strong interest in the arts, and he eventually enrolled at the Academy of Dramatic Arts. To support his studies, he worked at a Walgreen drug store. After graduating, he began his acting career, initially appearing in the 1951 film Teresa, a romantic wartime drama filmed in Italy.
Despite receiving positive reviews for his performance in Teresa, Ericson declined a studio contract, fearing typecasting as a "boy-next-door" type. Instead, he continued to work as a free-lance actor, appearing in a wide range of films and television shows.
Throughout his career, Ericson worked alongside some of the biggest stars of the time, including Elizabeth Taylor, Grace Kelly, and Spencer Tracy. He also had a successful television career, appearing in shows such as Rawhide, Burke's Law, and Bonanza.
In addition to his acting work, Ericson was a talented painter, sculptor, and amateur photographer. He was married twice and had a star on the Hollywood Walk of Fame.