Michael Richards, WFCA's chief executive, is to become chief executive of Ekay and Ekay's chief executive Eddie Powell will move into the role of managing director.
Ekay claims the deal makes it the largest agency outside of London by media billing.
WFCA's clients include Axa, Bupa, Carpetright and Ekay's clients include Ocean Finance and Dagenham Motors.
Richards said: "Both Ekay and WFCA can boast of having skilled and loyal staff who have already started working together on a range of projects which includes an invigorated marketing campaign to present the augmented offering to new and potential customers.
"While building revenues from our existing core clients is central to our strategy, we look forward to further opportunities to capture new business, to build on our base of national and international clients."
The acquisition is being paid for with £4m in cash and £4.5m in new Ekay shares to be issued by the company. The company is listed on London's Alternative Investment Market.
The transaction is conditional on the approval of Ekay shareholders at a general meeting on April 2.