The San Francisco-based firm offers 53 million local business reviews across 24 countries and attracts more than 120 million unique visitors a month. In March 2012 the company went public, valuing it at more than $6bn, and later the same year acquired Europe-based rival Qype, boosting its presence in the region.
Dynamo, which competed in a three-way pitch, will handle day-to-day press office work as well as creative campaigns incorporating the new tagline "We know just the place".
The agency will work with Yelp’s senior European PR manager Elliot Adams, who said: "Dynamo has already established a pedigree with Silicon Valley companies and prides itself on being ‘unboring’, one of Yelp’s core values."
Dynamo co-CEO Peter Bowles added: "Our team have a very broad remit to work across promoting the Yelp offering to consumers and helping small businesses realise the value in managing their free profile on Yelp for attracting further custom."
It's the first time Yelp has brought in a retained agency and previously has worked with a number of agencies on a project basis