As a student at the University of British Columbia, where he eventually received a bachelor’s degree in history and international studies, David Helliwell won a silver medal in the coxed eights at the 1956 Summer Olympics, alongside Philip Kueber, Dick McClure, Douglas McDonald, Bill McKerlich, Carl Ogawa, Waynne Pretty, Laurie West, and Robert Wilson. Two years later he won another silver medal, this time in the coxed fours event at the 1958 British Empire and Commonwealth Games with Don Arnold, Sohen Biln, Walter D’Hondt, and the non-Olympian Lawrence Stapleton.
Helliwell graduated from UBC in 1959 and coached there briefly before pursuing other career interests. He worked as a chartered accountant until 1965, and then turned to business, eventually serving on the boards of numerous institutions and organizations. He has been inducted into the Canadian Olympic (1958) and British Columbia Sports (1976), and University of British Columbia Sports (2010) Halls of Fame as a member of his silver medal-winning crew.