Born to Barnes Ratwatte Dissawa of Kandy and Rosalind Mahawelatenne Kumarihamy of Mahawelatenne Walauwa, Sirimavo was the eldest of six children, who included Barnes, Patricia, Macky, Sivali and Clifford. Her father, the Rate Mahaththaya, was actively involved in governance, whilst her mother in addition to playing the role of being housewife, was also known and appreciated for treating the villagers with Ayurvedic medicine. Spending most of her childhood in Mahawelatenna and Balangoda, young Sirimavo first attended a kindergarten school in Balangoda, continued to Ferguson High School, Ratnapura and then to St Bridget’s Convent, Colombo, where she was a Girl Guide for much of her schooling career.