Stephen McPhail scored his first goal since October to keep Cardiff's faint Coca-Cola Championship play-off hopes alive and put the skids on Hull's promotion charge.
McPhail's strike in the second minute ended a four-and-a-half-game goal drought in the league for the Bluebirds, who are now up to 12th in the table and eight points behind Hull who still occupy sixth place.
The former Leeds trainee crashed a close-range shot in off the underside of the bar after Steven Thompson had headed the ball into his path.
It was the first Championship goal Cardiff had scored since Gavin Rae's 45th-minute effort in the 2-1 home defeat to Norwich on February 9.
Cardiff's historic FA Cup run means they have games in hand over most of the teams above them and winning them would put them firmly in play-off contention.
The hosts maintained their bright start and continued to apply the early pressure as Thompson forced Tigers goalkeeper Boaz Myhill to tip his 18-yard shot round the post.
Hull had chances through Richard Garcia and Craig Fagan but neither worried Peter Enckelman in the home goal.
Henrik Pedersen and Garcia had goalbound shots blocked either side of the half-hour mark as Hull searched for an equaliser.
On loan Manchester United striker Fraizer Campbell looked to be the visitor's main threat in the first half, causing the Cardiff defence problems with his pace and movement.
Hull struggled to breakdown a resolute and organised home defence and were restricted to long-range shots. Ian Ashbee and Garcia missed the target with wayward efforts.
Ashbee should have done better than head straight at Enckelman from six yards out just before the hour mark.
Trevor Sinclair, one of three changes made by Cardiff boss Dave Jones following the cup win at Middlesbrough on Sunday, flashed an angled shot over the crossbar midway through the second half.
Thompson almost doubled Cardiff's lead in the 79th minute but Myhill again tipped his shot from the edge of the area round the post.
Teams
Cardiff Enckelman, McNaughton (Ledley 42), Loovens, Johnson,Capaldi, Whittingham, McPhail, Scimeca (Rae 62), Sinclair,Parry (Feeney 90), Thompson.
Subs Not Used: Oakes, Purse.
Booked: Capaldi, Loovens, Scimeca.
Goals: McPhail 2.
Hull Myhill, Ricketts, Turner, Brown (Clement 24), Dawson,Garcia, Marney, Ashbee, Pedersen, Fagan, Campbell (Hughes 68).
Subs Not Used: Tyler, Walton, France.
Booked: Turner.
Att: 17,555
Ref: Lee Probert (Wiltshire).