Black’s job at the year-old agency, which counts William Hill and the Wellcome Trust among its clients, will be to focus on new business and growth. She will start work at Fabula in the coming weeks.
Black, who has been at Fallon since January 2012, ran the Mondelez account. She joined the agency from Mother where she was a business director. Before that, she was an account director at WCRS.
She said: "In a consumer-led economy, brands owners are forever looking for exciting alternatives and new agency models. Fabula, to me, is the agency to offer that.
"After working for two of the greatest agency names in the business and working on big client names, I felt it was time for me to work on something new and groundbreaking and somewhat scary."
Former WCRS creative directors Yan Elliott and Luke Williamson launched Fabula, which is based on a barge in London, in June 2012. Elliott and Williamson have both previously worked with Black.