An investigation has been launched into the man’s death, who was arrested by Berlin Police along with some 600 other protesters.
Police said the man had complained of tingling in his arm and chest while officers checked his ID in the capital’s Mitte district. The officers proceeded to provide first aid until an ambulance arrived.
The man unfortunately died in hospital later that day.
Hundreds of people were detained at the protests this weekend, many of which had been banned by local authorities, including one from the Stuttgart-based Querdenker movement - the largest and most visible anti-lockdown movement in Germany - which expected 22,500 attendees.
Some 2,000 police were deployed around the city in an attempt to disperse the crowds.
The protests were widespread around Berlin and saw violent outbursts as protesters defied orders to disperse and tried to break through police lines.
A police spokeswoman said authorities were still trying to determine how many protesters and officers were injured during Sunday’s events, which were spread out across a large area.
Germany has relaxed many of the measures imposed during the height of the pandemic, but some requirements to wear masks indoors and present negative COVID-19 tests or certificates of vaccination are still in place.
Additional reporting by AP