The move follows BBC World-wide's acquisition of 75% of the company yesterday.The BBC believes that, over the next five years, the deal will boost web-related revenue by 10% and help to increase overseas revenue by two-thirds.
The acquisition of the Australian company was funded with part of BBC Worldwide's £350m borrowing limit. Founders Maureen and Tony Wheeler will retain a 25% share.
Lonely Planet currently publishes more than 500 titles. It sells 6.5 million books each year in 200 countries and also has a website, a web-based stock photography agency and a television production house, Lonely Planet Television.
A BBC spokesman said the transaction would not only be profitable, but would provide numerous publishing opportunities and increase the BBC's international presence.
"There is enormous scope for expanding Lonely Planet's output, particularly with online," he said. "Firstly, we will focus on dramatically increasing the range of content on the web, but there will be limitless opportunities to bring the Lonely Planet brand into other media.
"We are extremely excited, as this deal will bring together two of the world's best-known brands. Australia already receives a great deal of BBC programming and there is a real knowledge and love of the brand there. This deal will increase our presence in that market, as well as increase our profile in America, Canada and New Zealand.
"We have been looking for the right deal in Australia for some time now and, commercially, this is a coup for us. The opportunities for cross-fertilisation of content alone are immense."
The BBC has a broad programming slate, including Michael Palin's New Europe.
In a statement, the Wheelers said: "Joining BBC Worldwide allows us to secure the long-term future of our company within a globally recognised media group. BBC Worldwide provides a platform true to our vision and values, while allowing us to take the business to the next level."