The Hague-based body said it had rejected all financial claims made by Rwanda, which had argued Britain still needed to honour the terms of the deal which Prime Minister Keir Starmer cancelled in 2024.
After taking office that year, Starmer scrapped the prior Conservative government's asylum plan, under which Rwanda would have been paid to take in migrants who had illegally arrived in Britain.
Kigali was asking for at least £60 million ($A112 million), the court documents showed.
The three-judge panel found by a majority that in November 2024, Rwanda in diplomatic notes agreed "to forgo any additional payments by the United Kingdom in April 2025 and April 2026", the court said.
The details were released on Monday in excerpts of the ruling which the court said it made on May 15.
In the end only four people went voluntarily to Rwanda under the asylum agreement, which ran into legal challenges before its cancellation.
Relations between Britain and Rwanda soured in 2025 when London paused some aid over the Rwandan role in the war in Democratic Republic of Congo.
Rwanda has faced global pressure over accusations it supports the M23 rebel group in eastern Congo.
Kigali denies backing M23 and has blamed Congolese and Burundian forces for fighting that has killed thousands and displaced hundreds of thousands in the past year.
11°C