Janet Wickens, who spent more than five years at Perennial, will now lead a 15-strong in-house team responsible for fundraising, internal and external comms and publications. She will also manage the charity's external comms agency, Medialink.
After developing Perennial's fundraising and marketing functions, Wickens said she was now looking forward to the challenges presented by working for a much larger charity.
'As well as the obvious task of increasing voluntary income, one of my immediate aims is to dispel the myth that large charities are impersonal and do not care about the individuals they ask for help,' said Wickens.
'It's all about putting yourself in the place of the donor or volunteer.
With technology this is not difficult, but larger charities are often accused of missing the fact that each envelope is opened by a person.'
On the fundraising side, Wickens added she would be looking at corporate partnerships and making more use of the charity's donor database.
Wickens replaces Paul Alexander, who left Cats Protection in January to become chief executive of The Snowdon Award Scheme.