The Stop Brexit march, which has set off from the Art Gallery in Victoria Gardens, has been organised by Leeds for Europe and coincides with the one year anniversary of the triggering of Article 50.
Many in the good-natured crowd, which had come from all over the UK as well as abroad, had both Union and European flags draped round their shoulders.
The Headrow will be closed to traffic until the event finishes around 3pm.
The rally and speeches are listed to be at around 12.30pm outside Leeds Art Gallery.
Richard Wilson, chair of Leeds for Europe, said Leeds, which voted by 50.3 per cent Remain, was a "bellwether" for the country.
"There is lots in the media that implies it was because of people in the North supporting Brexit - we reject that claim," he said.
Mr Wilson said he had been moved to campaign against Brexit by the "frustration and anger" over the Leave decision, which he fears will cause "untold damage to our country."