The ads are set to be published in the part of the page which is used at the moment to display the most recent posts from popular users.
Mr Karp was recently interviews at a conference for Ad Age Digital, and he is reported to have said that he was a fool for saying that he was against online advertising. He had previously occused other social media who used advertising as being uncreative.
In yet another interview earlier this year, Karp told reporters that a last resort for Tumblr would be to start showing Google advertising, this would generate immediate income, but he says they are to explore other routes primarily.
Tumblr was launched in 2007, and due to its tremendous popularity with bloggers and meme creators it now boasts over 40 million indivual posts.