"Today we are about to start a new chapter of our story and we couldn't be more excited to share the news: Wildfire is joining Google!
"We truly could not think of a more perfect home for Wildfire."
A Google blog said "with Wildfire, we're looking forward to creating new opportunities for our clients to engage with people across all social services. We believe that better content and more seamless solutions will help unlock the full potential of the web for people and businesses."
The Wall Street Journal said Google had acquired the company for an as yet undisclosed price but its sources were confident of a figure around US$250 million.
Wildfire helps companies promote themselves through social media platforms such as Facebook, Twitter and Pinterest.
The company states on its website that it has over 16,000 clients, including 30 of the top 50 global brands.
The Wildfire blog said the company would operate "as usual" and there would be no changes to its service.