[2][3] Mercy was born in Kerala; her first international success came in 1981 Asian Championships in Athletics when she won the double bronze in the long jump and 4 x 400 metres relay.

[4] She represented India in long jump at 1983 World Championships in Athletics, but did not qualify for the final round.

[5] Mercy has the distinction of being the first woman from Kerala to win a medal in the Asian Track and Field meet.

[4] Her personal best in long jump is 6.29 m.[citation needed] In the latter stage of her career she switched to sprint and started competing in 400 metres.

Mercy and Murali were the first Indian athletic couple to be national champions and win Asian medals.