Forest had ended a five-game winless league run with victory over Peterborough prior to the international break.
Andy Reid scored the only goal of the game at London Road and it was the Irishman who opened the scoring here.
On-loan defender Daniel Ayala quickly added a second goal to give the hosts a 2-0 half-time lead.
Forest made sure of all three points shortly after the restart when Billy Sharp scored his first goal for the club since arriving at the City Ground on loan from Southampton seven weeks ago.
Heidar Helguson pulled a goal back for Cardiff midway through the second half, but despite Forest finishing the game with 10 men following Adlene Guedioura's red card for two bookable offences, they were unable to make any more inroads.
It meant back-to-back league victories for Forest for the first time this season, halting Cardiff's three-match winning run.
And the Welsh side also lost leadership of the table after Leicester came from behind to draw at midlands rivals Birmingham.
An uneventful game came to life after 25 minutes when Reid was fouled by Kevin McNaughton on the edge of the Cardiff box.
The Dubliner, who scored with a terrific curling effort at Peterborough a fortnight ago, repeated the feat with the resulting free-kick, bending a left-foot shot into the top corner and giving goalkeeper David Marshall no chance.
Two minutes later and it was 2-0 to Forest.
Ayala remained up in attack following a long throw from Greg Halford, and when Reid returned the ball into the box, the Norwich centre-half powered a header past Marshall from 10 yards out.
Helguson curled an effort over the crossbar as Cardiff sought an immediate response.
A nice move by Cardiff just before half-time then ended with the recalled Craig Conway falling over his own feet and Forest midfielder Chris Cohen clearing the danger.
Forest went further ahead two minutes into the second half.
Sharp held up the ball, spun his marker and ran at the Cardiff defence. He played a one-two with substitute Radoslaw Majewski, on at the break in place of Simon Cox, before shooting beneath Marshall for his first goal for the club.
Don Cowie saw a shot go narrowly wide as the visitors tried to respond.
Mark Hudson and Helguson missed chances to reduce Cardiff's arrears before the latter did so after 74 minutes.
Helguson controlled a high ball into the box, held off his marker and fired his shot beyond home keeper Lee Camp from 12 yards.
Cardiff were almost right back in it soon afterwards when the fit-again Tommy Smith struck a post with an effort from inside the area.
Had that gone in, it would have set up a frantic finale, particularly given Guedioura's red card in the 84th minute.
But Cardiff, despite some late pressure, were unable to make the game any closer and Forest claimed an impressive win.