Cassin began her broadcasting career working for Dublin pirate radio station Radio Nova in 1982, where she co-presented a nightly news programme, Dublin Today, with Bryan Dobson, later a fellow newscaster on RTÉ. In 1993, she presented Eurofocus, a RTÉ series on studies of education in European countries. She began presenting radio and television news bulletins for RTÉ in 1995 and has also covered current affairs, politics and sport as a reporter.
Cassin has also presented various non-news programmes including the weekly Dublin-based feature series Capital D, Crimecall and The All Island School Choir Competition. On 20 December 2011, she was named as the new co-presenter of Nationwide, replacing Michael Ryan. Her first Nationwide broadcast occurred on Friday the 13th of January 2012.
Cassin is the eldest daughter of the late actor and director Barry Cassin, and Nancy. She was educated at Loreto Convent, Balbriggan, Co. Dublin. Cassin has two children with her partner and RTÉ colleague Donagh McGrath.
- "CrimeCall: Anne Cassin". RTÉ. Archived from the original on 16 April 2009. Retrieved 14 April 2009.
- "Anne Cassin". Radio Nova. Archived from the original on 27 March 2009. Retrieved 14 April 2009.
- "Cassin is new Nationwide co-presenter". RTÉ. 20 December 2011. Archived from the original on 4 March 2015. Retrieved 20 December 2011.
- "Cassin's first Nationwide broadcast". RTÉ. 13 January 2012. Archived from the original on 4 March 2015. Retrieved 13 January 2012.
- Caden, Sarah. "Another stage of friendship". Irish Independent.