The agency won the pitch in a three-way final shoot-out against Bigmouthmedia and Greenlight.
Make It Rain will be responsible for Best Western's pay-per-click and search-engine-optimisation activity, which it aims to bolster throughout the year following the revamp of the Best Western website.
Last year Best Western was the first brand to run an advertising campaign on a Government site.
The month-long campaign ran on the revamped Met Office site for the first time. The ads were updated in real time to keep users informed on new offers and prices as they became available.
Best Western interim head of ecommerce and distribution Jason Munslow said: "Make It Rain showed great understanding of our brand and the travel sector and we believe they are the right agency to maximise our competitiveness against the many aggregators and other hotel chains."