The Gunners had taken a single point from their past five away league games and were without Pierre-Emerick Aubameyang, Mesut Ozil and Aaron Ramsey for Saturday's trip to Yorkshire.
Huddersfield, rock bottom of the Premier League, offered little resistance but did at least score for the first time since Jan Siewert replaced David Wagner as head coach thanks to Sead Kolasinac's late own goal.
Arsenal took the lead in the 16th minute. Kolasinac's deep left-wing cross found Iwobi and his volleyed finish took a decisive deflection off Terence Kongolo.
Henrikh Mkhitaryan almost marked his return from seven weeks out with a foot injury with a goal but he could not beat goalkeeper Ben Hamer at the end of a flowing Arsenal move.
But he was involved in Arsenal's second before the break, Mkhitaryan teeing up Ainsley Maitland-Niles for a driven low cross that Lacazette tapped in at the back post.
Huddersfield almost replied in the 50th minute but Adama Diakhaby's driven effort from a low Kongolo cross was saved comfortably by Bernd Leno.
Iwobi should have added his second after Mkhitaryan fed him but he fired his shot into Hamer's chest, while Leno denied Diakhaby again and Huddersfield's home debutant Karlan Grant had an effort cleared off the line at the other end.
And the Huddersfield fans finally had reason to celebrate after four games without a goal as Kolasinac turned into his own net in the 93rd minute, while Leno then saved from Juninho Bacuna to protect the Gunners' victory.
What does it mean? Arsenal still in top-four race
The battle for Champions League qualification looks set to go to the wire, with a single point splitting United in fourth and Arsenal in sixth, although Chelsea have a game in hand.
Huddersfield's survival chances are ever more desperate as a 13-point gap to make up in just 12 matches, considering their almost total lack of goal threat, appears an increasingly impossible equation.
Mkhi shines on return
The absence of Ozil and Ramsey created a spot for Mkhitaryan and the Armenia international was lively, if understandably a little rusty, on his return to action. If the Gunners are to finish in the top four and also push for the Europa League crown, Mkhitaryan will have a big role to play.
Hamer error gives Huddersfield mountain to climb
Deflected goals usually give goalkeepers little chance, but Hamer seemed to have time to react after Iwobi's weakly struck shot hit Kongolo. The goalkeeper, making a fourth Premier League appearance of the season deputising for Jonas Lossl, reacted too late to stop the tame effort.
Key Opta Facts:
- Arsenal are the only side without an away clean sheet in the Premier League this season.
- Sead Kolasinac's own goal was Huddersfield's first goal in 597 minutes of football in all competitions, since Steve Mounie scored against Burnley in January.
- Arsenal won their fifth away Premier League game of the season, one more than they managed on the road in the whole of 2017-18.
- Huddersfield are the first side to lose seven consecutive home Premier League games since Wolves in April 2012 (a run of nine).
- Alexandre Lacazette netted his first away goal in 10 games for Arsenal in all competitions, since scoring twice at Fulham back in October.
- Alex Iwobi has had a hand in 10 goals in all competitions for Arsenal this season (four goals, six assists), his best return in a single campaign for the Gunners.
Arsenal's next two games are both in the Europa League as they take on BATE in the last 32, with the Gunners returning to Premier League action at home to Southampton on February 24. Town, who are also out of the FA Cup, are away to Newcastle United a day earlier.