Talman, who has been with the New York-headquartered firm for six years, is to leave on 20 January. Crozier will leave just four days afterwards.
Talman said: 'I am keeping an open mind as to what to do next. I want a fresh challenge and a new environment. I am considering a lot of things.'
Crozier, who joined just over two years ago from a board director role at Cohn & Wolfe UK, said: 'I've had a challenging but rewarding time – it's now time to embrace something new.'
The duo would not rule out starting afresh in tandem.
CCA's 45-strong London office has roughly doubled in size in the past three years. Its annual fee income surged by 35 per cent during 2004 to £3.3m – an almost seven-fold increase on fee income levels six years ago.
Gail Cohen has relocated from CCA in New York to fill Talman's shoes on an interim basis.
Co-founders Bob Chandler and Gianfranco Chicco, both usually based in the US, will take it in turns to be stationed in London during the recruitment process.
In addition to hunting a permanent replacement for Talman, CCA is also now recruiting for the newly created role of Europe head of practice.
CCA was highly commended in the Specialist Consultancy of the Year category at October's PRWeek Awards.
CCA clients include Novartis, Pfizer, Merck KGaA, Schering-Plough, UCB, Allergan, Merck Sharp & Dohme and AstraZeneca.
Staff at CCA's London office were informed of the imminent exits last Thursday.