But the friendly at the Mestalla threatened to be overshadowed by Jose Gaya's red-card horror tackle on Anthony Elanga, which saw the Newcastle winger stretchered off in the first half and led to both sets of players clashing.
Fortunately for the Sweden international, his injury does not appear to be serious, with Elanga later up and walking after a contusion to the shin.
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A stunning fifth-minute opener from Valencia's Filip Ugrinic and then Elanga's injury gave Jaissle a nightmare start to life in the Newcastle dugout.
But his half-time changes sparked a Toon turnaround with new signings Bazoumana Toure and Sean Steur impressing.
It was last summer's signing Wissa who pounced on a mistake to level in the 52nd minute.
New arrival Toure then broke clear of the Valencia defence to unselfishly set up Wissa for a tap-in to complete the comeback in the 76th minute.
Toure should have had a second assist after fine work down the left, but Jacob Murphy put over his cross in stoppage time.
The win brings some relief to Newcastle on the day they lost their captain Bruno Guimaraes to Arsenal.
Jaissle's next pre-season test will come on Wednesday as his new side face Everton at Murrayfield in Edinburgh.
Wissa's fresh start under Jaissle
Sky Sports News' Keith Downie at the Mestalla:
"A good end to a positive week in Spain for Newcastle - and a trophy for Jaissle in his first match in charge as they lift the 'Orange Cup'.
"Some impressive signs from new signings Aladji Bamba, Steur and Toure.
"Newcastle's travelling fans sent home from The Mestalla with a spring in their step.
"One major positive was Wissa's performance.
"Newcastle really need him to come good this season. It was a huge £55m outlay on a 29-year-old, and last season was a nightmare for him.
"He looks sharp and is coming off a good World Cup showing. Maybe this could be a fresh start for the striker."
