The Terriers finished fifth last season, 13 points behind Championship winners Newcastle, and needed a penalty shoot-out to overcome Reading in the play-off final at Wembley.
But they have made themselves feel instantly at home in what is their first appearance in the top flight since 1971-72, thumping Crystal Palace 3-0 away from home last weekend.
And they made it two wins from two attempts thanks to Aaron Mooy's emphatic 50th-minute strike at a packed John Smith's Stadium.
While Wagner and his buoyant players can do no wrong, Newcastle have endured a difficult return to the highest level, Rafael Benitez now having overseen successive defeats following a 2-0 loss at home to Tottenham in the opening round of the campaign.
The former Valencia, Liverpool and Real Madrid manager, after watching his team come off second best against a heavily reinforced Huddersfield side, will no doubt feel his own club's lack of transfer activity must be addressed with less than two weeks remaining before the window closes on August 31.
Huddersfield's familiar high-tempo approach had caused Newcastle problems from the outset, Mooy testing Rob Elliot from long range after just four minutes.
Tom Ince also called the visitors' goalkeeper into action, turning and shooting first time and on the half-volley after Christian Atsu had carelessly given the ball away.
Despite the hosts' early dominance, Newcastle came agonisingly close to breaking the deadlock in the 16th minute, Ayoze Perez teeing up Matt Ritchie, whose curling strike to the far post was brilliantly saved at full stretch by the diving Jonas Lossl.
Undeterred, the Terriers resumed their determined approach to the contest, energetic centre-forward Steve Mounie forcing a turnover in the Newcastle box to create a chance for Ince in the 27th minute, but the former Derby County attacker's shot was blocked.
Although Benitez's side - missing the suspended Jonjo Shelvey following the midfielder's sending off against Spurs - slowly managed to take the sting out of the game as the half wore on, Huddersfield had the last opportunity of note before the break, Philip Billing winning possession in a dangerous area and leading a promising counter-attack, only for Chancel Mbemba to smuggle the ball behind for a corner.
Huddersfield managed to assert themselves early in the second half and deservedly broke the deadlock through influential midfielder Mooy. The Australia international exchanged a clever one-two with Elias Kachunga to create space for himself at the top of the penalty area and curled a brilliant finish beyond the reach of the outstretched Elliot.
2 - Two of Aaron Mooy's five league goals for Huddersfield have come against Newcastle (both at the John Smith's Stadium). Rasper.— OptaJoe (@OptaJoe) August 20, 2017
Newcastle responded well to falling behind and nearly equalised in the 67th minute.
First the intervention of Lossl was required to deny substitute Joselu and then, from the subsequent corner, Ciaran Clark's header fell to Perez, who somehow blazed over unmarked from close range.
That was as close as the away team came to snatching a point, leaving Huddersfield to reflect on their swift adjustment to life among the elite ahead of an EFL Cup tie at home to Rotherham United, followed by the visit of Southampton in the league next Saturday.
Newcastle play host to Nottingham Forest in midweek, before a showdown with fellow winless side West Ham next weekend.