The telecoms giant said a boost in the numbers signing up for its services meant it achieved a 93% share of all broadband net adds during the three-month period to the end of September.
But new chief executive Gavin Patterson warned that any celebrations would be premature as it faced the challenge of keeping up its early success in the wake of the start of the top-flight football deal in August.
BT has paid £738 million to show 38 games a season, including Scottish matches, for three years and revealed that it has also invested £140 million over the latest quarter - as it starts to count the cost of producing programme content.
Mr Patterson hailed the positive impact the sport offering was having on the business.
But he cautioned: "It's too early to crack open the champagne. It's made a good start but we need to make sure that that continues in future quarters."
BT added a net 156,000 users over the period, nearly double the figure for the same period last year, taking the total to around seven million.
Mr Patterson said a 4% growth in consumer revenues for the quarter was the first rise in 10 years, boosted by a 17% increase in broadband and TV turnover following the sports channel launch in August.
BT said it had narrowed line losses to 65,000, an improvement on last year and better than some City forecasts. Growth of 70,000 in BT TV - where customers watch via a BT set-top box - saw numbers reach 900,000.
Its figure of two million BT Sport customers includes those who can watch via satellite, BT TV or online via an app. But the reach extends to a total of four million households when potential Virgin Media viewers are included.
Investment in sport helped operating costs rise 8% and hit underlying earnings but overall pre-tax profits grew 2% to £609 million. They had been expected to fall but were buoyed by better figures elsewhere, including depreciation and financing costs.
Mr Patterson said there had been a "real push" for the early phase of BT Sport but acknowledged it would be "difficult to hold those results all the way through from here".
He added: "We have to be judged on whether our consumer business is growing over the medium term."
Mr Patterson was non-committal over speculation that BT could be preparing to bid for Champions League football.
He said: "We don't feel as though we need to have any more live rights. We'll evaluate them and if they are going to create value for the group, we are going to be interested in them."
Richard Hunter, head of equities at Hargreaves Lansdown stockbrokers, said: "The take-up of BT Sport from existing customers, as well as its contract with Virgin Media, puts the company in front of a whole raft of consumers.
"This has, of course, come at a cost, and investment in the new foray into sport has provided a drag on overall earnings.
"On balance, though, the company's prospects continue to whet the appetite of growth investors. BT remains a company in transition but it already has extremely firm foundations in place for further progress."
Earlier this month analysts at UBS downgraded shares in the telecoms giant amid concerns that it has overestimated the size of the market for its TV sports channels as it vies with Sky over football coverage.
BSkyB has so far shrugged off the competition, announcing earlier this month that record numbers tuned in to the start of the football season - with an average audience of 1.55 million compared with 1.29 million last year.
Recent figures show BT has achieved average audiences of 588,000 for Premier League matches, less than the 641,000 average achieved last season by ESPN.
But it points out that it has a higher audience share, averaging 4.95% of around nine million viewers watching TV at lunchtime when its games are shown, compared to ESPN's 2.8% of a total teatime audience that was twice the size.