A third of these young millennials also admit to regularly watching illegal streams, compared to just 4% of over-35s, according to a survey of 1,500 UK consumers conducted by SMG Insight on behalf of the BT Sport Industry Awards.
As reported by SportBusiness Group, while young millennials are just as interested in professional sport as the rest of the population, their viewing habits show a number of differences.
For example, just 14% of millennials are likely to have paid for a sports subscription channel, compared to 24% of non-millennials, and they are also more likely than older generations to use OTT services, such as NOW TV (although the proportion remains small at 5% versus 2% of non-millennials).
"The polling shows that sport is still captivating for audiences of all ages. But what continues to change is the way younger people consume their sport," said Nick Keller, Chairman of the Sport Industry Group, which organises the BT Sport Industry Awards.
"Unless we are careful, we will have a generation of young people who consider pirated sports content to be the norm. That's a significant challenge not just for rights holders but the whole sector – from sponsors and athletes to ticketholders," he added.
"It's in everyone's interests, not least the fans who enjoy a quality product, to make sure that the value of sport is maintained by delivering a quality product through the best means to appeal to the audience."
Elsewhere, the survey revealed that millennials, like the rest of the population, still prefer to view sport live on TV, with just 2% opting to watch sport as clips on social media.
In addition, traditional broadcasters like the BBC and Sky remain the main provider of sports content for all groups, although 11% of young millennials prefer online sources like Twitter and Facebook.
Richard Brinkman, MD of SMG Insight, said of the last two findings: "That millennials are moving to other mediums comes as no surprise. But what is interesting is that the pace of change remains slow and that traditional forms of sports consumption – like sitting in front of a big TV – remain by far the favourite option."
Data sourced from SportBusiness Group; additional content by WARC staff