The FTSE 100 publishing group, which also owns Heat magazine and radio networks Kiss and Magic, has handed Brunswick the business in place of incumbent Financial Dynamics.
Brunswick pitched against rivals Tulchan Communications - founded by former Brunswick partner Andrew Grant - Citigate Dewe Rogerson and FD.
The agency will report to group communications director Miranda Acland, who oversaw the pitch.
Acland confirmed Brunswick would be targeting sell-side analysts and journalists to communicate EMAP's corporate messages to those in the City.
Brunswick partners Louise Charlton and Patrick Handley will lead the account.
FD loses out on the remit after five years heading the City PR business.
Brunswick will work with Emap to communicate strategy as CEO Robin Miller continues his mission to get the firm back on an even keel.
The company's most high-profile financial issue of the last year has been its ill-fated attempt to enter the competitive US publishing market.
EMAP paid close to a billion pounds for publishing company the Petersen Group, before being forced to write-down almost two thirds of the value of the investment - only £365m was eventually clawed back-in its most recent financial results.
The impact of this loss led to the resignation of the then chief executive Kevin Hand and his replacement with Miller,a former journalist and editor of EMAP title Motorcycle News who was CEO for over a decade until 1998 but stepped up to the chairman's seat on the appointment of Hand.