Zac Sapsford, dropped to the bench after six goalless games, came on as a second-half substitute and scored in the 58th minute on Saturday night, extending the Wanderers' unbeaten run to 11 games.
As a result, Alen Stajcic's side move to third on 43 points, behind premiers Auckland FC (50) and Melbourne City (45), and ahead of Melbourne Victory (42) and Western United (41).
City drew 0-0 with Adelaide United (seventh, 38 points) on Saturday night, while Auckland face Perth and Western host Sydney FC (37) on Sunday.
The top-ranked Australian team receives an Asian Champions League Elite berth, while first and second have the opening week of finals off.
Western Sydney next play Macarthur FC, who are out of the finals race, in Campbelltown next Saturday.
In-form attacker Nicolas Milanovic was once again excellent for the Wanderers at McDonald Jones Stadium.
"That was the motive today, I think, just to look at that finals spot for us and to put pressure on City tonight," Milanovic told Paramount Plus.
"So, yeah, good luck to them, but we want that second spot."
In the 17th minute, Brandon Borrello released Milanovic into space, but the in-form winger shot straight at Jets goalkeeper Ryan Scott.
Two minutes later Milanovic headed wide after a good ball from Gabriel Cleur.
In the 33rd minute, Milanovic forced a near-post save from Scott, then nodded another chance wide a minute later.
Borrello missed a golden opportunity when he dragged a shot wide in the 48th minute.
But eight minutes later he pounced on a loose pass from the Jets and squared it for Sapsford to tap home.
Sapsford should have made it 2-0 in the 71st minute, but his close-range shot was weak and Scott saved with his feet.
Lachie Rose missed a golden chance to equalise two minutes later, receiving a cut-back from Eli Adams but blasting his shot wide of the near post.
The Wanderers believed Newcastle defender Aleksandar Susnjar should have seen red when he brought down Sapsford as the striker got through on goal in the 74th minute, but he escaped with a booking.
While the Jets pushed for an equaliser, the visitors' defence wouldn't be breached.
Newcastle finish their season away to the Victory next Sunday, playing their last game under Rob Stanton.
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