Grimaldi just finished his second full season, he only played four games as a true freshman, at the University of North Dakota. The 21-year-old finished the 2013-14 NCAA campaign with a team-leading 17 goals, 22 assists and 39 points. The goals and points were career-highs. He was named Most Valuable Player at the Midwest Regional, where the Fighting Sioux knocked off Wisconsin and Ferris State. North Dakota was defeated in the Frozen Four by the University of Minnesota.
His career totals at UND were 31 goals, 46 assists, and 77 points in 86 games. He also showed a combative side by accumulating 68 PIM.
Internationally, Grimaldi picked up a gold-medal at the 2013 World Junior Championship, where he bagged the tournament-winning goal against Sweden. He picked up another gold as a member of the 2010 U.S. team that captured the U18 World Championship.