MacDonald was a member of the bronze-medal winning American team at the 1986 World Junior Hockey Championship. He took a year off from Harvard in 1987-88 to play member of the United States' 1988 Winter Olympics team in Calgary. MacDonald would return to Harvard as team captain to win the 1989 Hobey Baker Award, given to the top collegiate ice hockey player, while at Harvard University, and leading the Crimson to the NCAA Championship. After college, he played for HC Lugano is the Swiss League before recurring migraine headaches forced him to retire. He attempted a brief comeback with the 1992 US Hockey team in preparation for Albertville Olympics, but left competitive hockey for good prior to the Winter Games. He then went to Stanford Business School and is now a General Partner in a Boston area private equity firm, where he lives with his wife and three children.