After drawing with Chelsea and beating Manchester City, Phil Brown's side had appeared to be edging towards mid-table respectability but, with other results going against them, the Tigers once again look set for a relegation scrap in the last three months of the season.
Blackburn have only lost twice at Ewood Park all season and, despite a few anxious moments in the closing stages, deserved their eighth three-point haul of the campaign.
After Boaz Myhill has made a superb reflex save from Ryan Nelsen's close-range header, Rovers took the lead in the 16th minute when Martin Olsson collected a pass from Morten Gamst Pedersen before cutting into the penalty area along the byline.
From the tightest of angles the Swede beat Craig Fagan and fired a low shot through Myhill's legs, the effort taking a slight deflection off the keeper before nestling in the back of the net.
Hull responded well but were reduced to ten men before half-time when George Boateng was adjudged to have elbowed Pedersen. It seemed a harsh decision and it effectively ended the game as a contest.
Myhill was forced to tip Gael Givet's close-range header onto the bar but the Tigers also went close through Jan Vennegor of Hesselink and Stephen Hunt.
Brett Emerton wasted a good chance to double Rovers' advantage, shooting straight at Myhill after being put through by El Hadji Diouf but, in the final analysis, it was of no consequence as Blackburn held on to claim the victory that lifted them up to 11th in the table.