On July 9, 2006, Preissing and Josh Hennessy were traded by the Sharks to the Chicago Blackhawks for Mark Bell. Chicago immediately traded the two, along with Michal Barinka and a second-round draft pick in the 2008 NHL Entry Draft, to the Ottawa Senators in exchange for Martin Havlát and Bryan Smolinski. Preissing then spent the 2006–07 season with Ottawa, recording 38 points in 80 games and posting the third-best plus-minus rating (+40) of any NHL player. He helped the Senators reach the Stanley Cup final, in which they lost to the Anaheim Ducks in five games.