The Manchester City striker turned in from close range to give Norway the lead on 29 minutes in Boston, but Aymen Hussein’s header brought Iraq level.
Haaland pounced on an error at the back to put Norway ahead again before half-time and take his goals tally at international level to 57 in just 51 matches.
Leo Ostigard headed in a third for Norway moments after coming off the bench to effectively wrap up victory. Norway got a fourth deep into stoppage time through a Hussein own goal.
The win left Norway on top of Group I on goal difference, level with France on three points after Les Bleus overcame Senegal 3-1 earlier in the day. The Norwegians face the African powerhouses in their next game in New Jersey on June 22.
No team endured a longer or more perilous road to the World Cup than Iraq, who secured their place as the 48th and final qualifiers in March after a 21-match campaign that stretched across 867 days.
Hussein, scorer of the decisive goal in the play-off win over Bolivia, was held and questioned for hours by US immigration officials after arriving with the squad ahead of Iraq’s first World Cup since 1986.
Norway last played at the tournament in 1998, when coach Stale Solbakken was a member of the squad that famously beat Brazil in the group stage before exiting in the last 16. He also featured at Euro 2000.
After breezing impressively through qualifying, twice thrashing Italy, they are hoping a golden generation of players – led by Haaland and Arsenal midfielder Martin Odegaard – can break new ground in North America.
Solbakken predicted Haaland would make a “very big impact” at his first major finals, and the City star was quick to deliver on that promise.
Antonio Nusa’s trickery was a problem for Iraq, and his incisive pass released the overlapping David Moller Wolfe clear before Haaland stretched to steer in the low cross from the left.
Iraq, who lost all their of group games on their only previous appearance, did not let that get to them as they equalised 10 minutes later.
Amir Al-Ammari found space just inside the area and clipped in a cross, with Hussein rising brilliantly to power a header past Orjan Nyland.
But Iraq only had themselves to blame as they gift-wrapped Haaland’s second of the contest.
Goalkeeper Jalal Hassan was slow to react to a softly hit back-pass, his attempted clearance smacking off Haaland’s shin and ricocheting into the net.
Iraq again responded well with Ibrahim Bayesh denied by a desperation block, Ali Al-Hamadi dribbling an effort wide and centre-back Akam Hashim lashing a spectacular volley just over the bar.
Ostigard nodded in Odegaard’s corner on 76 minutes to seal the points for Norway, before Haaland was thwarted by Hassan when another loose pass sent him clean through and seeking his hat-trick.
Haaland nonetheless had a hand in Norway’s late fourth, his looping header back across goal deflecting off Hussein before trickling over the line. (AFP)
