The competitive pitch process, reported first by Campaign, was run by Oystercatchers and handled by Alison Dean, head of consumer marketing for the UK at Savills.
Isobel has been asked to "develop a new creative positioning across all channels".
Savills previously worked with The Red Brick Road for five years but the pair ended the relationship because of a client conflict.
In May, The Red Brick Road was hired to handle the creative and PR activity for easyProperty, the online estate agent that is part of Sir Stelios Haji-Ioannou’s easyGroup as it expands into the residential sales market.
Dean said: "At what is a very exciting time for the property industry, Savills, as one of the most established and recognised brands within the sector, is looking forward to working with Isobel."