He played eight seasons as a left winger in the National Hockey League (NHL) with the St. Louis Blues, Phoenix Coyotes, Dallas Stars, and Los Angeles Kings.

After being drafted Nagy came to North America and played with the Halifax Mooseheads on the QMJHL for the 1998–99 season and was named the fans 7th most popular player during the 15 year celebrations.

Nagy played with the Blues then from 1999 to 2001, and was traded to the Coyotes with Michal Handzus, Jeff Taffe and a first round pick in the 2002 draft in exchange for Keith Tkachuk.

On February 12, 2007, Nagy was traded to the Dallas Stars for winger Mathias Tjärnqvist and a first-round pick in the 2007 NHL Entry Draft.

[7] In December 2010, Nagy signed for Swedish strugglers Modo Hockey for the rest of the season, joining compatriot Ľuboš Bartečko at the club.