The assignment followed a competitive pitch.
Anna Shardlow, head of brand and digital engagement at Crisis, said: "For people experiencing homelessness, Christmas can be an incredibly difficult and isolating time of year. We need to shine a light on the challenges and day-to-day realities people without a home face."
The agency's clients include Adidas, CALM, PlayStation, FIFA, John Lewis & Partners, Lloyds Bank, Volkswagen and Mars.