Injury-hit Hull made them work hard in difficult conditions and scored two tries in the last quarter through Tom Saxton and Gareth Raynor to set up a nerve-jangling finish before the Rhinos held on for a valuable opening-day success.
Tries from threequarters Marcus Bai, Chev Walker and Keith Senior helped Leeds set a new club record of 14 Super League games without defeat and extended their unbeaten run against Hull to 10 matches.
The champions deserved their win but Hull, lacking six regulars through injury, emerged with considerable credit and managed to dominate both the opening and closing exchanges.
They had the champions under all sorts of pressure at the start, with winger Bai losing possession inside his own �22� and Danny McGuire knocking on in front of the posts.
But Leeds defended heroically and on the counter-attack twice almost seized advantage of makeshift full-back Motu Tony�s vulnerability under the high ball.
The kick was always going to be a potent weapon in the slippery conditions and it proved the route to the first try of the half on 20 minutes.
McGuire�s punt ricocheted into the grateful arms of Chris McKenna and McGuire and impressive full-back Richie Mathers worked the ball out sweetly for Bai to touch down at the corner.
Kevin Sinfield added a priceless conversion from the touchline, a kick which grew in importance when Hull loose forward Paul Cooke fluffed a comparitively straight-forward penalty on 24 minutes.
A string of penalties enabled the Rhinos to step up the pressure and it paid off when dangerous centre Walker took a flat pass from dummy half Andrew Dunemann on 30 minutes to score his side�s second try.
Sinfield�s second conversion made it 12-0 but Cooke pulled two points back with a penalty four minutes before half-time after Willie Poching had been pulled up for interference.
Hull also had a glimmer of a chance when stand-off Richard Horne intercepted Danny Ward�s on half way but he slipped on the treacherous surface before he could get into his stride.
As the rain, which restricted the crowd to a healthy 17,080, continued to fall, the Rhinos� 10-point lead began to look increasingly impressive.
And there seemed no way back for Hull when the champions increased their advantage on 52 minutes thanks to an immaculately-created third try.
Seven men handled in a flowing crossfield move but it was an offload from the tackle by McKenna that did the damage as centre Keith Senior took Poching�s pass to cross the line wide out.
Hull continued to battle away, with hard-working skipper Richard Swain thrown back from the line and debutant Tom Saxton dropping Graeme Horne�s pass within sight of the corner.
Saxton made amends on 62 minutes when he followed up Cooke�s clever grubber kick that bounced awkwardly in the in-goal area to score try.
Cooke added the conversion to cut the deficit to eight points and, when Raynor took Cooke�s overhead pass to slide over at the corner five minutes from the end, doubts began to surface over the champions� composure.
Indeed, the visitors breathed a huge sigh of relief when the unfortunate Saxton knocked on at a play-the-ball just short of their line with six more tackles in the bag.
Hull: 12 (2) Tries: Saxton, Raynor Goals: Cooke (2)
Leeds: 16 (12) Tries: Bai, Walker, Senior Goals: Sinfield (2)
Hull: Blacklock, Yeaman, Raynor, R. Horne, Lupton, Dowes, Swain, McMenemy, Cooke, Tony, Thackray, Saxton, Chester.
Higgins, Dixon, McNicholas, G. Horne, Hill.
Leeds: Mathers, Calderwood, Walker, Senior, Bai, McGuire, Burrow, Bailey, McDermott, Lauitiiti, McKenna, Sinfield, Dunemann.
Ward, Poching, McDonald, Jones-Buchanan, Ellis.