TVNZ also recorded an additional 61,700 streams, adding to the overall viewership.
The average audience calculated over the course of the full running time of the programme came in at 657,800 viewers.
So how does this compare to previous elections?
From an overall reach perspective, this is on par with 1.1 million viewers who also tuned in for the first debate between then-National leader Bill English and Labour leader Jacinda Ardern.
The level of engagement in the 2017 debate did, however, come in slightly higher, with the average audience tallying 784,000 over the course of the programme.
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• Leaders debate a ratings winner for TVNZ
The first debate of 2017 would ultimately deliver the best ratings, with viewership coming lower for the Newshub follow-up and TVNZ's final round.
The lead up to the 2017 debate had an element of controversy, with New Zealanders questioning the decision by TVNZ to appoint Mike Hosking as the moderator.
This culminated in a petition attracting 76,000 signatures demanding that TVNZ remove Hosking as the adjudicator.
Despite the outrage, TVNZ decided to stick with their initial choice.
This year's choice of John Campbell didn't attract nearly as much controversy, but the veteran presenter's predecessor Hosking did offer some critical feedback, saying that Campbell's style was too languid and that he didn't do enough to keep the politicians on their toes.
With the first debate out of the way, the attention will now turn to round two, which is set to air on Three next Wednesday, with the politicians facing off under the moderation of Paddy Gower in front of a live studio audience.
After a relatively measured outing somewhat akin to a pair of wiley heavyweight boxers finding their feet in the first round, the pressure will now be on for them to land a few solid blows.