Browne has been at the agency for just 12 months, joining from The Martin Agency where she held the same role. She previously worked at Channel 4 and Abbott Mead Vickers BBDO.
Grey staff were made aware of her forthcoming departure in an all-agency email from chief executive Leo Rayman. He paid credit to her for launching Greyfest and bringing in the Metropolitan Police as a client.
In a statement, the agency said: "Olivia Browne will be leaving in June due to family circumstances. We’d like to thank Olivia for the dedication she’s shown to the agency over the last 12 months and wish her well in the future. We’ve started the process of finding a replacement."