Spark says "almost 60,000" streamed the World Cup opener.
"This makes it one of the highest viewed live-streamed sport events in New Zealand and a record for Spark Sport," the telco said in a statement.
It did not immediately reveal how many paid between $60 and $90 for a Tournament Pass, and how many gained access via a free offer for qualifying Spark customers.
Rival Sky earlier claimed 55,000 streams for the second Bledisloe test in August (see below).
Quoting Nielsen figures, TVNZ says its coverage of the opening ceremony and the opening clash between hosts Japan and Russia reached a total 5+ audience of 983,000.
There were a number of complaints on social media, but Spark said there were no system-wide issues and that an estimated "less than 1 per cent." had problems. Some were a problem with Samsung TVs that required a restart, others with incorrect setup on the user's part, the telco said.
Newstalk ZB producer Mark Kelly, who lives in Auckland, said he watched the opening ceremony and first half of the match with no problems.
But when he quickly turned over to check the rugby league before going back for the second half he saw a message saying there were technical problems and never saw another second of the game.
Kelly was on the phone to Spark Sport for an hour but was told the supervisor had gone home.
A tougher test is to come. Spark Sport head Jeff Latch has long said tonight's All Blacks-South Africa clash will draw the biggest streaming audience - his logic being that the AB's other pool games (and, likely, their quarter-final) are against soft opposition, while both semis and the final will be live on TVNZ.
Unlike the opener, which was also screened live on free-to-air partner TVNZ, the All-Blacks South Africa game will only be available live via Spark Sport (TVNZ will carry it on a one hour-delay - see the full lfree game schedule here).
How Sky's numbers compare
Last month, Sky said the second Bledisloe test was streamed by 55,000 via its Sky Go and Sky Sport Now (formerly Fanpass) apps. A further 523,400 watched the match on Sky decoders, while 408,000 watched the delayed version on Prime and an estimated 100,000 followed the match in pubs and clubs.
And earlier this month, Sky said 23,000 streamed the All Blacks RWC warm-up vs Tonga.
Industry talk has it that Spark paid around $13 million for World Cup 2019 rights (or roughly double what Sky paid for the 2015 tournament) with around $1m defrayed by free-to-air partner TVNZ.
That figure implies the telco needs around 133,000 Tournament Pass buyers just to cover its content rights costs - although Spark also regards the RWC as its foot in the door for mainstream sports streaming, and its ultimate success could depend on how many stay loyal to its regular $20 a month service, and any new content broad on board, after the RWC.
Spark says it won't comment on RWC costs until its first financial results post-RWC (expected in February).
The telco has sought to manage expectations, from its earlier admission that some people in rural areas just didn't have good enough broadband for streaming the RWC to its last-minute warning to some small-town customers yesterday that they needed to upgrade their plan.
The telco says it has taken a number of steps to fill the gaps, including offering the RWC to pubs and clubs at its residential price, and making a Tournament Pass free to rural schools, which often have fibre and can act as community viewing hubs.