Kypreos struggled to score at the NHL level and immediately became known as an enforcer, a role he maintained throughout his pro career. He was never drafted by an NHL team, but was signed as a free agent by the Philadelphia Flyers on the eve of his second junior season. However, his NHL career began with the Washington Capitals. His best NHL season came in 1992–93 while a member of the Hartford Whalers, when he scored a career-best 17 goals while earning 325 penalty minutes, which was the fourth-highest penalty minute total in the league that season.[citation needed]
He made his final NHL stop with his hometown Toronto Maple Leafs. As a Maple Leaf, his career ended as the result of a concussion sustained in a fight with the Rangers' Ryan VandenBussche in a pre-season game on September 15, 1997 when his face hit the ice after he was punched unconscious. After the injury, Kypreos suffered from post-concussion syndrome and was forced to retire.[2][3] He finished his NHL career with 46 goals, 44 assists, 90 points, and 1,210 penalty minutes in 442 regular season games.[4]