The Government has pledged two million euro in funding to provide life-saving food, shelter, basic healthcare and water to some of the most vulnerable communities in Africa.
Some 8.5 million people need urgent humanitarian assistance in both countries, with ongoing conflict driving people to flee their homes, particularly in border areas between Sudan and South Sudan.
Minister Costello said that July 9 marks the second anniversary of the independence of the Republic of South Sudan.
"It is the world's newest State," he said. "While we welcome the progress made since 2011, many communities remain extremely vulnerable to disease and food shortages as a result of decades of conflict and chronic underdevelopment. More than four million people do not have access to enough nutritious food. "
Mr Costello said the UN estimates that 4.4 million people need assistance in Sudan, with 3.5 million people in Darfur in desperate need of emergency food assistance.
"While there has been progress, with 200,000 displaced people returning to their homes in Darfur, almost 1.5 million people continue to live in temporary camps," he added.
"The assistance I am announcing today will provide food, shelter, basic healthcare and education to the worst-affected communities in both countries and help to safe-guard the gains made in recent years."