In 1978, she married Vijaya Kumaratunga a leading actor and LSSP turned SLFP political activist. She supported his election campaign in the by-election in Mahara in 1983, where he lost in the recount. She left the SLFP in 1984, when Vijaya Kumaratunga formed his own party the Sri Lanka Mahajana Pakshaya (SLMP) supporting his political activities against the policies of the mainstream parties. She served as the Vice President of the SLMP. This resulted in her falling out with her mother and brother who were leading the SLFP at the time. On 16 February 1988, Vijaya Kumaratunga was assassinated in front of his home in Narahenpita by gunmen in the presence of his wife. Chandrika Kumaratunga briefly took over the leadership of her husband's party, and formed the United Socialist Alliance with the Communist Party of Sri Lanka, the Lanka Sama Samaja Party, and the Nava Sama Samaja Party. Although it was well organized, it lacked votes. Fearing for her life, she soon fled the country in 1988, seeking refuge in the United Kingdom. There she worked for World Institute for Development Economics Research at the United Nations University. During her absence the SLMP had split into two factions during this time and had ousted her from its leadership.
Chandrika married movie star and politician Vijaya Kumaratunga in 1978, who was assassinated on 16 February 1988, outside his residence in the presence of Chandrika and their two children, then aged five and seven.