After signing the deal, interim Prime Minister, Arseniy Yatsenyuk had strong words for Russia, who he says is trying to break his country apart.
Fresh aid for Ukraine was signed off in Brussels.
The EU pledged more than $1.8 billion dollars to help improve government institutions in Kiev, and pay off state-owned debts to Russian gas suppliers. In exchange Ukraine has promised public reforms.
The EU has promised ongoing support, Xinhua reported.
"Ukraine can count on the European Union now and in the future," European Commission President Jose Manuel Barroso said.
The EU deal is one of several financial lifelines extended to Ukraine by western nations, including aid from the United States, and a 17 billion dollar package from the International Monetary Fund.
The EU has tried to help Ukraine in other ways, too, by temporarily lifting customs duties on Ukrainian exports to the EU and reversing the flow of natural gas from Slovakia to Ukraine as an alternative to Russian supplies.
Ukraine also will sign a free trade deal with the EU in June.
It is all part of a broad effort to prevent Ukraine from defaulting on its debts at a time of grave political instability.