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.