"Based on data from user's interaction with Bing, we have seen that mobile users are able to satisfy their information needs much faster on searches that return more mobile-friendly results," said Microsoft's Shyam Jayasankar in a blog post.
"With that in mind, we will be rolling out mobile friendliness as a signal in ranking."
Microsoft said however that mobile friendliness would be just one of the factors considered when displaying search results.
"This means that for mobile searches on Bing, you can always expect to see the most relevant results for a search query ranked higher, even if some of them are not mobile-friendly," said Jayasankar.
He said pages that are highly relevant to a search will not get penalized even as mobile-friendly pages get a boost.
Changes are expected "in the coming months."