On Saturday 8,000 people answered a joint call by far-right party AfD and Islamophobic Pegida movement to march once again on the streets of the former communist city in Saxony state.
The mobilisation vastly outnumbered a contingent of 3,000 counter-protesters, including Green and Social Democratic Party MPs.
Local police, backed up by officers from across Germany, were out in force to keep both sides from clashing.
But, as the rallies cleared, scuffles took place among small groups.
Police are examining at least 37 possible offences, including bodily harm, property damage and resistance against law enforcement officers.
On Sunday two smaller demonstrations against xenophobia passed off without disturbances.
Chemnitz has been in the spotlight after violent far-right protests erupted over the fatal stabbing of a 35-year-old man, allegedly by a Syrian and an Iraqi, last Sunday.
Foreign Minister Heiko Maas called on Germans to take a stand against xenophobia.
"We have to get off our sofas and open our mouths," he told the Bild am Sonntag newspaper. stressing that "all of us have to show the world that we democrats are the majority and the racists are the minority."
"The silent majority must get louder," he said.
Despite the tension in Chemnitz, racism is not the norm for Germany, RFI's Berlin correspondent Emmanuelle Chaze says.
NGOs, artists and politicians have been actively organising counter-protests on social media and holding rallies across the country.
Bands Kraftwerk and Die Toten Hosen are to lead a free concert against racism in Chemnitz on Monday evening.
The tensions in Chemnitz have underlined the divisions in Germany over Chancellor Angela Merkel's decision three years ago to keep Germany's borders open to asylum seekers, many fleeing war in Syria and Iraq.