In the absence of top scorer Pierre-Emerick Aubameyang through illness, Lacazette played a lone role through the middle for Arsenal and had a sight of goal as early as the ninth minute, only for Terence Kongolo to thwart him with a last-ditch tackle.
Iwobi shot into the side-netting from a tight angle on 11 minutes, but was celebrating his third Premier League goal of the season shortly after, thanks in part to an unintentional assist from Kongolo.
The Nigerian was left in acres of space at the back post and found by Henrikh Mkhitaryan's cross. The subsequent volley would have been easy pickings for Ben Hamer had it not taken a big deflection off his own defender.
Huddersfield matched Arsenal between the two boxes but it was the same old story that has plagued them this season, during which they have only scored six home goals in the top flight, as they lacked the cutting edge to seriously trouble Bernd Leno.
The hosts could arguably have had a penalty on 22 minutes when Jason Puncheon's volley from the edge of the box was blocked by a combination of Laurent Koscielny's arm and chest, with referee Jonathan Moss giving Arsenal the benefit of the doubt.
Arsenal's main threat came from the right flank, from which Ainsley Maitland-Niles teed up Mkhitaryan on 40 minutes, but the Armenian's shot lacked the power to truly test Hamer, who was deputising in the Huddersfield goal for the injured Jonas Lossl.
Maitland-Niles was the provider when the Gunners notched what turned out to be a crucial second before the break, his overlapping run and cross supplying an unmarked Lacazette with a simple back-post finish for his 10th league goal of the campaign.
The Terriers found themselves in a similar position to that of last weekend when they went on to lose 5-0 to Chelsea, but they did not show any signs of another capitulation as they dominated second-half possession with 66%, while creating a few more chances.
Juninho Bacuna had a couple of efforts from distance, hitting one straight down Leno's throat and dragging the other wide. Good play down the left yielded an opportunity for Adama Diakhaby, who hit the target from 12 yards out but not with enough conviction, allowing Leno to scramble across his line to make the save on 50 minutes.
Diakhaby looked like the player most likely to find Huddersfield a way back into the game but a precious goal escaped him again as he turned an attempted shot from Puncheon wide of the post from inside six yards.
Iwobi should have put Arsenal out of reach on a 71st-minute counter-attack, but Hamer stayed big to block from the goalscorer, who had been played through by Mkhitaryan.
Depoitre was involved again when his 50-50 with Leno broke to Karlan Grant, whose shot was cleared off the line by Nacho Monreal, but Huddersfield's luck in front of goal finally changed on 93 minutes when Kolasinac bundled the ball into his own net following Leno's save from Diakhaby.
Huddersfield's fans were able to celebrate their first goal in six matches but it was not enough to snatch them a point.
HUDDERSFIELD (4-3-3): Hamer; Smith, Schindler, Zanka, Kongolo (Durm 56'); Hogg, Mooy, Bacuna, Puncheon (Depoitre 66'); Diakhaby, Kachunga (Grant 83')
ARSENAL (4-2-3-1): Leno; Maitland-Niles Koscielny, Mustafi, Monreal; Torreira (Elneny 59'), Guendouzi; Kolasinac; Mkhitaryan (Suarez 76'), Iwobi (Willock 88'); Lacazette
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