Andrea Fonseka was born in Penang, Malaysia on Ausgust 29, 1984. She is of mixed ethnic heritage. Her father is of Sinhalese (Sri Lankan), Portuguese, Spanish, and Filipino descent, while her mother is of Chinese descent She is the youngest of four daughters and currently lives and works between Singapore, Malaysia and Australia.
Her surname is the Sinhalese variation of the surname "Fonseca", which has its origins in Portugal and was introduced by settlers to Sri Lanka. The surname in its original Portuguese form is often associated with Sephardic Jewish origins.
She married Australian lawyer Paul Alexander Dewar on 31st July 2010.