The summer signings ended their lean spells to play a prominent part in a win that boosts Middlesbrough's prospects of a top-six finish.
Manager Steve McClaren had kept faith with his misfiring strikeforce and insisted all along that the duo would soon return to goalscoring form.
Viduka grabbed a brace against Manchester City with Hasselbaink adding a third.
With Middlesbrough leading 3-1 after 65 minutes it looked as though three points were in the bag.
The visitors however fought back when the introduction of Bradley Wright-Phillips paid an immediate dividend.
Bradley, the 19-year-old brother of Shaun Wright-Phillips, marked his Premiership debut with a goal after being on the field only five minutes.
The goal galvanised City and it took a magnificent Mark Schwarzer save to deny Joey Barton an equaliser three minutes from time.
Dutch international Michael Reiziger made a long awaited comeback for Middlesbrough after an early season shoulder injury.
But Boro were without the suspended George Boateng and Franck Queudrue while Chris Riggott was a late withdrawal with a hamstring injury.
The injured Nicolas Anelka was a major loss for City for whom Danny Mills received a warm pre-match welcome from the home fans who remembered his role in the Carling Cup triumph last February.
Viduka opened the scoring after nine minutes when he coolly chipped the ball over David James. It was his first goal after a 12-match barren run.
City hit back and from a Jonathan Macken header Robbie Fowler darted forward and left Schwarzer helpless as his close-range shot hit the Boro keeper on the way in.
Viduka was on target again after 54 minutes after a slick one-two with Hasselbaink. Shortly afterwards Hasselbaink hit a superb free-kick round the wall and into the net, giving James no chance.
Despite a memorable moment for Bradley Wright-Phillips, Boro deserved the victory as they remained fifth in the Premiership.