Morawiecki was attending a two-day summit of European leaders in Brussels. Just hours before the meeting, Britain and the EU agreed a deal under which they can divorce.
Morawiecki said the agreement would secure the rights of Poles in Britain and the interests of Polish companies, for which Britain is an important export market.
The impact of Britain’s shock 2016 decision to withdraw from the EU has been closely watched in Warsaw as there are around a million Poles living in the UK, constituting that country’s largest minority community.
The agreement on Brexit, hammered out during weeks of talks, has to be backed by both the British and European parliaments.
But the Democratic Unionist Party in Northern Ireland, which British Prime Minister Boris Johnson needs to help ratify a deal, has said it cannot support the agreement.
Johnson wants to secure backing for the deal in the British parliament on Saturday in order to pave the way for an orderly divorce on October 31.