Chasing 183 for victory, Lucknow looked in trouble at 54-2 in 8.2 overs but Mankad's 64 and a series of key partnerships including an unbeaten 58-run stand with left-handed Pooran guided the Super Giants to victory over Hyderabad with four balls to spare.
Mankad, an up-and-coming batsman, first set the pace with a 73-run partnership with Marcus Stoinis, who hit a 25-ball 40.
Mankad raced to his maiden IPL fifty and then changed gears with Pooran, who scored a rapid 44 off 13 balls.
The West Indian smashed three consecutive sixes in a 31-run over as Lucknow moved into the top four to bolster their playoff hopes.
See the full scorecard on Flashscore.
South Africa's Heinrich Klaasen stood out with 47 for Hyderabad, in an innings interrupted by crowd trouble as the home team lost momentum and finally the match to stay in ninth position.
Things got heated in the crowd after Hyderabad's Abdul Samad, who hit an unbeaten 37, received a waist-high delivery that was called a no-ball by the on-field umpire but overturned on review.
The delivery appeared to be above the batsman's waist but Lucknow reviewed it in their favour, cancelling out the run and the free hit.
Home fans got into an altercation with the Lucknow dugout, prompting a stoppage of play, with Klassen dismissed a ball later.
"Disappointed by the crowd, to be honest, that's not what you want," said Klaasen after his 29-ball knock.
"That also broke the momentum, not great umpiring either, but you can't take matters in your own hands."
The no-ball decision was slammed by experts including Tom Moody, who tweeted, "How can the 3rd umpire take that long to make the wrong decision?"
Lucknow skipper Krunal Pandya returned impressive figures of 2-24 as he struck on successive balls to take down his counterpart Aiden Markram, for 28, and Glenn Phillips, for a duck.
