The president of the European Commission was seen being supported by other leaders and was also seen at the event in a wheelchair.
It’s not the first time the 63-year-old has been spotted struggling to walk and in the past he has blamed sciatica, which causes numbness in the legs.
World leaders met in Brussels to discuss a number of issues but the main item on the agenda was defence spending.
Donald Trump criticised Nato, taking aim at many of the US’s allies, insisting they should all hit the 2 per cent of GDP target put forward by the alliance.
Mr Trump called an unexpected press conference during the summit where he claimed he had made alliance leaders agree to new commitments.
“I let them know that I was extremely unhappy with what was happening,” he said.
“And, as a result, they are going to up it to levels like they have never thought it before. What they are doing are spending at a much faster clip.
“The additional money they had agreed to put up has really been amazing… some are at 2 per cent, others have definitely agreed to go to 2 per cent and some are going back to get the approval and which they will get to 2 per cent.”
Within minutes of the press conference ending, a number of alliance members said they had simply agreed to keep to the spending commitments which had already been made.
A spokesperson for the European Commission said they would not comment on personal health issues.