The deal with the architecture and design publishing business is the Danish group's first acquisition outside Scandinavia and is a major step in its international expansion.
The acquisition, which comes a few months before Dezeen's 15th birthday, reinforces its position as a leading architecture and design magazine.
"I'm proud of what Dezeen has achieved over the past 15 years and I'm convinced that JP/Politiken Media Group is the best possible partner for the brand's future," said Dezeen founder and editor-in-chief Marcus Fairs.
"We want Dezeen to forever be a bastion of independent journalism, a champion of architecture and design and a force for good in the world," Fairs wrote in a first-person article explaining the reasons for the sale of the business he launched as a bedroom startup in 2006.
"To this end, we have found a soul mate in JP/Politiken Media Group. I look forward to working with the group over the coming years to develop and grow the brand."
Owned by two private trusts, JP/Politiken Media Group is committed to social responsibility and believes that journalism is vital to democracy. A shared belief in these principles was a key driver of the deal, says Dezeen.
"A democratic society is built on free and independent media," says the group. "It is vital for society that citizens have independent, reliable, and stable media that they can trust."
Fairs launched Dezeen as a simple blog in November 2006. Working from his spare bedroom, he started out with no investment, no business knowledge and no technical skills, yet Dezeen has grown every year since and now employs 28 people in London.
Fairs, a journalist who previously launched and edited architecture and design print title Icon, was joined by his partner Rupinder Bhogal, a former TV production manager, in 2008. Together as co-founders they built the business into what it is today.
"Building Dezeen has been a real adventure and we are hugely grateful to our readers, our business partners and particularly our team," said Bhogal. "We couldn't have got this far without them. We're looking forward to the next phase of our journey together with JP/Politiken Media Group."
As part of JP/Politiken Media Group, Dezeen will retain its editorial independence and leadership, with the senior management team remaining in place.
Fairs will stay at the helm of the brand as its CEO and editor-in-chief and Bhogal will continue as HR director. Chief content officer Benedict Hobson and chief revenue officer Wai Shin Li will continue in their roles.
Together they will work with JP/Politiken Media Group to grow the business and develop its content offering.
"We are thrilled and honoured to join Marcus and Rupinder in the future development of Dezeen as the world's leading media for architecture and design," said Anders Heering of JP/Politiken Media Group.
"With great passion, dedication and unwavering confidence in quality journalism, the two founders and their very talented team have built up an impressive brand that, we believe, continues to hold plenty of unrealised potential."
Anders, together with special adviser Peter Normann, will form Dezeen's new board of directors alongside Fairs and Bhogal.
JP/Politiken Media Group is one of Denmark's leading media groups. Formed by the merger of two private trusts, it exists to "equip citizens with facts and knowledge that make them better able to take an active part in a democratic society."
Keep up-to-date with publishing news: sign up here for InPubWeekly, our free weekly e-newsletter.