Former Downing Street aide, Jude MacKenzie, is to join the charity in September as associate director of advocacy and communications.
MacKenzie will be in charge of more than 100 staff members across media, publishing, global advocacy and policy, campaigns, information and internal comms.
The move ends her four-year stint as director of comms at the Commission for Social Care Inspection.
Before that, she worked closely alongside former Downing Street comms chief Alastair Campbell as strategic comms adviser at the Prime Minister's office. She has also led brand development and comms at the NHS.
Christian Aid conducted a strategic comms review after Phillips left. The charity's marketing function was moved out of the comms remit to the marketing and supporter relations department, while international comms was moved in.
The appointment comes as Christian Aid gears up to increase its fundraising activities and comms output.
Director Daleep Mukarji, to whom MacKenzie reports, said: 'There are unprecedented challenges ahead as we see the impact of climate change, the food crisis and many other difficult problems.'
The charity has just signed 3 Monkeys to handle media for its Christmas gift aid catalogue, following a three-way pitch.