Fiddler beat Nikolai Khabibulin from the edge of the crease after getting open and taking a pass from Alexander Radulov, who was behind the net.
Scott Nichol added an empty-net goal with 42.6 seconds left, and Nashville won its third straight game and ninth out of 10. Rookie defenceman Kevin Klein scored his first NHL goal for the Predators, who lead the NHL with 73 points and 35 victories.
Nashville's Tomas Vokoun stopped 30 shots.
Brent Seabrook scored for the Blackhawks, who lost their 10th straight (0-8-2) overall and eighth consecutive at home (0-6-2). Their last victory was Jan. 2 at St. Louis and their last win at the United Center was Dec. 26 over Dallas.
Khabibulin made 28 saves for Chicago.