Hull clinched their second win in the south of France to extend their winning run in the engage Super League to 11 matches and move to within two points of leaders St Helens.
Peter Sharp's men, who triumphed 34-28 in Perpignan in April, were given another tough test in Narbonne before securing victory with two tries in the last quarter.
The kick-off was brought forward to enable the French to watch their team play in the World Cup quarter-final and Hull raced into a 12-0 lead after 17 minutes.
Captain Richard Swain came up with a break and full-back Motu Tony continued play for leading scorer Richard Horne to finish off by touching down for the ninth successive game.
Great Britain winger Gareth Raynor added a second try five minutes later and Paul Cooke added his second conversion to make it 12-0.
Dragons back rower Ian Hindmarsh burst through to score from a Chris Beattie pass and winger Justin Murphy added a second 10 minutes before the break after intercepting a pass by Tony and racing 90 metres.
Stacey Jones' conversion cut the deficit to 14-10 at half-time, Cooke having added a penalty to his two conversions.
Jones then levelled the scores with a solo try nine minutes into the second half and added the conversion to put his side in front for the first time at 16-14.
The French had their chances but Hull struck a decisive blow on 59 minutes when Horne sliced through the home defence to set up a try for substitute Shaun Briscoe and centre Sid Domic made sure of the win with his side's fourth try three minutes from the end.