YPlan
The startup, founded in 2012, was backed by investors to the tune of $37.7 million (£31 million).
But the event ticketing company has been struggling in recent months, letting go of a third of its workforce and scaling back its US operations in February.
As a result, it's unlikely that YPlan's investors will see a return on their investment.
"Developing e-commerce and monetising our audience is an important element of our ambitious growth strategy," said Julio Bruno, chief executive of Time Out Group, according to City A.M.
"We acquired YPlan because its advanced technology will significantly accelerate this strategy. It will enable us to offer our large audience more online booking opportunities, whilst improving the user experience.
"We look forward to welcoming the highly skilled YPlan employees to the Time Out team. Together we will be stronger than ever to bring our customers the capabilities to make the most of the city and to make Time Out an even better place to discover, book and share."
YPlan's founders Rytis Vitkauskas and Viktoras Jucikas said: "Today is an exciting day for YPlan as we become part of Time Out, a global media and entertainment company. Both companies are an excellent fit.
"For us as founders, the acquisition is a natural continuation of our vision for YPlan: to enable people to discover and do amazing things, whether in their beloved home cities or while traveling. We're both very proud to join with our team such an iconic brand and to be part of Time Out's next chapter."
Shares in Time Out Group jumped 13% in mid-morning trading.
Time Out and YPlan are yet to respond to Business Insider's request for comment.