On Wednesday, she won a nine-year term on the tribunal that adjudicates disputes arising over the UN Convention on the Law of the Sea (UNCLOS) and agreements between countries that give it jurisdiction.
The tribunal was set up in 1996 and is based in Hamburg, Germany.
Chadha was the only candidate from the Asia Pacific Group to be elected in the first round of elections where the 168 countries that are parties to UNCLOS voted.
Judge P. Chandrasekhara Rao, the Indian currently on the tribunal, completes his second nine-year-term this year. He served as the President of the tribunal from 1999 to 2002.
Chadha was the first woman to be the chief legal adviser to the Indian government and her career includes stints as an additional secretary in the External Affairs Ministry and a counsellor at India's UN Mission.
Chadha, who is a legal consultant to the Indian government, has experience of ITLOS from the other side of the bench.
She successfully represented the country before the tribunal in the case brought by Italy demanding the release of two of its marines charged by India with killing two Indian fishermen.
The tribunal refused to order their release.
In the maritime borders dispute between India and Bangladesh, she represented New Delhi at the Permanent Court of Arbitration in The Hague. The verdict awarding Bangladesh 19,467 sq.km of the contested area in the Bay of Bengal was seen as a victory for Dhaka.
She also represented India in a frivolous case brought in the International Court of Justice (ICJ) by the Marshall Islands over what it said was New Delhi's failure to end the nuclear race.
The ICJ dismissed the Marshall Island's case.
She has studied at the University of Michigan Law School.
The tribunal has one woman judge, Elsa Kelly of Argentina, and another, Liesbeth Lijnzaad of the Netherlands, was elected on Wednesday along with Chadha.
Kriangsak Kittichaisaree of Thailand was elected by the Asia Pacific Group in the second round of voting.
In elections to another international legal post, Aniruddha Rajput was elected by the UN General Assembly to the International Law Commission last November.
At the International Court of Justice, Judge Dalveer Bhandari's term ends next February. The judges have a nine-year term, but he was elected to a six-year term to fill a vacancy.
(Arul Louis can be reached atAarul.email@example.com)