He becomes the first ECD at the agency and takes over creative output from creative director Dan Evans, who left in June.
Beer will work alongside the AllTogetherNow management team of Conor McNicholas, chief executive; Steve Parker, managing director; Flora Proudlock, head of strategy; and Tom Sneddon, business director.
In his new role, Beer has been asked to "redefine" the agency’s offering and build the creative department’s profile.
Beer joined Don’t Panic last year, having previously worked for the agency on a freelance basis since 2013. He worked on the Save the Children "Most shocking second a day" campaign, which picked up a gold Cyber Lion at Cannes in 2014.