Hall, who started at the newly privatised postal service last week, will work with head of public affairs David Gold.
She was previously at MHP Communications, where she worked for eight years managing clients including Laing O'Rourke, Crossrail and Camelot.
Her appointment comes after an interim period following the departure of her predecessor Alice Dickerson, who moved to the BBC earlier this year as senior public affairs adviser.
Hall joins Royal Mail Group at the busiest time of year for the organisation as Christmas approaches, and in the wake of the company’s flotation on the stock exchange in October in a £3.3bn deal.
The company’s share price has surged more than 80 per cent since its first day of trading, and it will be joining the FTSE 100 index of blue-chip companies.