Following their 1-0 win over second placed Hull on Tuesday, Gianfranco Zola's side failed to keep pace with their rivals following a frustrating evening.
The point for City leaves them requiring a maximum of seven points from their remaining six games as they take a step closer to the Barclays Premier League.
Zola made two changes to the side that edged past promotion rivals Hull on Tuesday. Former Arsenal goalkeeper Manuel Almunia returned between the posts while stalwart defender Lloyd Doyley was also recalled.
The Bluebirds made just one change following their 3-0 win against lowly Blackburn over the Easter weekend. Striker Joe Mason came in to replace the injured Fraizer Campbell.
Malky Mackay's preparations suffered a huge blow 10 minutes into the game though when Kevin McNaughton was forced to replace Matthew Connolly at the back.
However, they started the brighter of the two sides and Bo-kyung Kim soon forced Almunia into a fine save as he blocked a low effort with his feet.
Craig Conway then fired just wide from the edge with the hosts struggling for a response as they waited for a chance to counter.
Cardiff came closer still as Ben Turner headed over the top before Zola's gameplan began to pay dividends.
Top-scorer Matej Vydra nodded down for strike partner Troy Deeney but he inexplicably blazed his strike over the bar from no more than 10 yards.
The Hornets penned their opponents deep in their own half and with the game bubbling nicely things threatened to boil over on the touchline. Zola's assistant, Giancarlo Corradini, had to be pulled away by the little Italian after clashing with Mackay as they argued over Aron Gunnarsson's challenge on Cristian Battocchio.
Referee Mark Halsey kept his cards in his pocket and Cardiff managed to keep the ball out of their net as they survived a late onslaught before the break.
The visitors responded positively after the restart and Almunia did well to save Joel Ekstrand's blushes pushing away Joe Mason's strike after he seized on an error by the defender.
As the game began to open up David Marshall was forced into action at the opposite end making a terrific fingertip save to keep out Deeney's header.
Conway fired a volley narrowly wide before Hornets substitute Fernando Forestieri lashed one inches over the crossbar as the game continued at a frantic pace.
The former Udinese man then squandered another promising opportunity as he dragged another effort wide from the edge after a clever flick by Nathaniel Chalobah.
Cardiff were forced to try and utilise Gunnarsson's long throw in the closing stages and it very nearly paid off when Kim's close-range effort was deflected wide of the post.
Mackay's former charges looked as though they might have the last word when Deeney found a way through but he was crowded out before he could get a shot away.
Forestieri also saw his shot bravely blocked over the top during a frantic final few minutes but in the end both sides were forced to settle for a hard-fought point.
PA