She joined the agency in early 2015 after stints at The Academy, Unity and Mischief.
Vardon (pictured), who left Golin on Friday last week, said: "After almost four years at Golin, I’ve decided it’s time to move on. My aim when I started was to build the creative culture of the agency and improve the quality of work across teams - and I’m pleased I’ve been able to do that.
"I’m now looking forward to a new challenge, working with other agencies over the next few months and splitting my time freelancing between London and Brighton."
Golin London MD Bibi Hilton said: "Gemma has decided to leave her permanent ECD role at Golin to return to freelancing. She has made a huge contribution to Golin in her four years here and we look forward to that continuing in a freelance role next year."
Vardon is a mentor on the new Creative Mentoring Project from PRWeek and the PRCA Creative Group.
Earlier this month, Golin announced a global "repositioning" in which it "proudly" calls itself a PR agency.
PRWeek reported in February that a number of senior figures had left Golin’s London office, including marketing and talent lead Jane Fordham and head of digital Alex Brittain.