Gayle poked the ball home from close range on 22 minutes after the hosts' goalkeeper Rob Green had dropped Jack Colback's high, hopeful strike from distance, giving Rafa Benitez's side the advantage at Elland Road.
And nine minutes into the second half he made it two, sliding in to covert Vurnon Anita's low cross to notch his 13th Sky Bet Championship goal of the season as the Magpies made sure of the points.
United were first to threaten in the fourth minute, when Matt Ritchie stepped over Jonjo Shelvey's low corner from the right, presenting Anita with a shooting opportunity. The Dutchman's shot from the edge of the box was blocked, though, and Benitez's side were unable to profit from the resulting corner.
Shelvey's quick thinking then gave leading scorer Gayle his first sight of goal. The ex-Liverpool playmaker caught the Leeds defence off guard with a well-weighted free kick, but goalkeeper Rob Green was quick off his line to get himself in the way of Gayle's shot.
And midway through the half, they made a deserved breakthrough through former Crystal Palace frontman Gayle. From just inside the Leeds half, midfielder Jack Colback struck a speculative, looping effort towards goal which had Green backpeddling. With the ball about to drop just under the crossbar, Green got a hand to it but was unable to hold onto the ball, and Gayle pounced from close range to prod home the opener.
It was an instinctive effort from the 26-year-old, and barely a minute later the visitors could have made it two when Yoan Gouffran curled just wide.
Full back Luke Ayling called Karl Darlow into action on the half hour, forcing the Newcastle custodian to tip his looping header over the top, but that was as close as Leeds came to a leveller in the first period.
Three minutes after the restart, Darlow was tested again by Eunan O'Kane, who robbed Colback and took aim, but the Irishman saw his low drive saved.
However, they were punished for their profligacy on 54 minutes, when good work from Ritchie and Anita down the right culminated in the latter sending over a low cross, which Gayle slid home for his second of the afternoon.
Ayling cut inside and saw a left-footed shot deflected over as Garry Monk's men sought a way back into the contest, but the United rearguard held firm. A lofted cross from the lively Kemar Roofe went over the head of Paul Dummett and found Souleymane Doukara at the far post, but he couldn't direct his header into the bottom corner, and Darlow saved comfortably.
Gayle was withdrawn by Benitez with just over ten minutes left on the clock, with Aleksandar Mitrovic sent on in his place. Within minutes of his introduction, he drew a foul from centre back Pontus Jansson, who was fortunate not to pick up his second yellow card.
And despite some late Leeds pressure, Newcastle saw out the game to ensure they would return to Tyneside with all three points and a clean sheet in the bag.
