Miguel Almirón had levelled the scores for the Magpies after the break, following Rafinha’s first half opener at St. James’ Park.
But Harrison responded for the visitors with a deft finish which proved to be the winner, despite what was a spirited second half showing from Steve Bruce’s side – particularly following the introduction of Allan Saint-Maximin.
After Jonjo Shelvey dragged an early shot wide, Leeds carved out the first real chance of the game when Stuart Dallas picked out Harrison at the far post, but his first-time volley backfired as he sliced it horribly.
But before the half way point in the first period the visitors had the lead. Jacob Murphy, back in the side in place of Javier Manquillo, lost possession and Patrick Bamford played in Rodrigo on the right. The Spanish international was forced wide but managed to cut back and pick out Rafinha in the centre, and his finish was low and precise.
Newcastle began to grow into the half after the opening goal, though, with Jamaal Lascelles heading a Shelvey corner wide and Ryan Fraser blazing a Murphy cross high over the bar as Bruce’s side rallied.
But Leeds retained a significant threat on the counter and before the break, Rafinha almost made it two. It was a rapid breakaway which also involved Rodrigo, who couldn’t quite find the angle to get a shot away, but his Brazilian teammate did, thumping the upright with a cross shot.
Rodrigo and Murphy then exchanged wayward attempts at either end but after the restart, Leeds almost had a freakish second goal. It came from another Rafinha break, and his cutback found Dallas whose shot was charged down. The ball cannoned back off Dallas’ arm and looped over Darlow, clipping the crossbar before bouncing down beyond the line, but following a VAR check referee Anthony Taylor disallowed the goal.
Miguel Almirón, who replaced Andy Carroll in the line-up, shot straight at Illan Meslier and Lascelles glanced another Shelvey delivery off-target, but just before the hour the hosts had a leveller. It came from the Paraguayan but owed much to a fine tackle from Lascelles, which handed Shelvey possession, and his cross was delicately flicked into Almirón’s path by Wilson. The finish was low and just too powerful for Leed’s French goalkeeper Meslier to keep out.
It got Newcastle back on level terms – but for just a few minutes. Rafinha was again the architect on the break, as his perfectly clipped pass found an unmarked Harrison on the left, and his sweetly-struck finish flashed across Darlow and nestled in the far corner.
Allan Saint-Maximin was then introduced from the bench, making his first appearance of the calendar year after recovering from COVID-19, and the chances continued to come for both sides. Rafinha fed substitute Tyler Roberts, whose flick was kept out by Darlow, before Saint-Maximin fed Jamal Lewis, whose strike clipped the crossbar on its way over. Lascelles then went close with a header which also struck the woodwork in what was becoming a breathless, end-to-end second half.
Saint-Maximin was looking very lively on his return, and his work led to a corner which Shelvey met, but Meslier palmed it over. Fabian Schär went on an adventurous run which took him all the way to the edge of the Leeds box, but the visitors’ stopper parried the eventual shot.
The Magpies were firmly on top in the closing stages, and Dwight Gayle whipped a free kick over the top inside the final ten minutes, but though they applied plenty of pressure, United couldn’t quite find the equaliser they needed.
