"The IMF board took the decision to grant Ukraine one billion dollars," wrote Petro Porochenko on his Facebook page, seeing it as "another sign of the reforms under way in Ukraine."
Cash-starved Ukraine has been desperately waiting for the next instalment of a USD 17.5-billion rescue programme that has been held up repeatedly since it was agreed in 2015 over delays by Kiev to carry out reforms.
The IMF had delayed its decision on the next loan instalment, originally scheduled for March 20, saying it needed to reassess the "implications of recent developments for the programme".
The postponement came after Kiev's pro-Western leadership in March imposed a trade blockade on Russian-backed rebel-held eastern regions.
The head of Ukraine's Independent Association of Banks in Ukraine Roman Shpek has said that nearly all the money would go into refinancing the former Soviet republic's outstanding debt to the IMF.