He played in the National Hockey League (NHL) with the St. Louis Blues from 2002 to 2007.

He was selected by the Blues in the seventh round, 253rd overall, in the 2001 NHL entry draft.

Internationally he played for the Czech national team at several tournaments, including the 2002, 2006, and 2010 Winter Olympics, winning a bronze medal in 2006, and several Ice Hockey World Championships, winning gold medals in 2000, 2001, and 2005.

[2] On February 26, 2007, Čajánek was placed on waivers, but he was not claimed by another NHL team and remained with St.

On October 21, 2007, Čajánek signed a one-year, $900,000 contract to play for Ak Bars Kazan in the Russian Superleague (RSL) for the 2007–08 season.