The city is split over whether a democratic nation such as Germany should be erecting monuments that are paid for, designed and built by an authoritarian one such as China.
The divide spilled into the streets with duelling demonstrations for and against the monolith, forming a noisy backdrop to the statue's official dedication.
On one side, hundreds of flag-waving members of Germany's fringe Communist Party cheered. On the other - separated by barricades and riot police - an eclectic group of Free Tibet, anti-Fascist and pro-human rights protesters chanted and blew whistles in a vain effort to drown out the speeches.
City officials say they see nothing wrong with the statue's unusual path to Trier's downtown. The statue, Trier Mayor Wolfram Leibe insisted, is not about the "glorification" of Marx. Instead, he told the large crowd that had assembled under a cloudless blue sky, it's meant to spark conversation - and strengthen international bonds.
"It's a gesture of friendship," he said.
But others in Germany - a nation divided for nearly a half-century due in no small part to its native son's theories - say city officials are being naive about a project that neatly aligns with Chinese state propaganda.
"There's no doubt that there's a political agenda behind it," said Christian Soffel, a Chinese studies professor at Trier University.
How important Marx is to that agenda was underlined by the visit of two senior Chinese officials who spoke at the ceremony. The officials - the country's ambassador to Germany and the deputy chief of the Information Ministry, the government's propaganda arm - each paid tribute to Marx, though not in terribly Marxian terms.
The ambassador, Shi Mingde, said China had "modernised" Marx's theories - a veiled reference to the country's hearty embrace of much of modern capitalism - and boasted that China is responsible for 30 per cent of global economic growth.
"For that," he said, "we can thank Karl Marx."
At the unveiling's critical moment, Chinese and German officials together pulled back a red drape to reveal a rendering of Marx in full stride - a book clutched beneath his left arm, his right gently pressed to his signature frock coat.
Not so long ago, Germany was tearing down statues of Marx. An icon of communist East Germany, his likeness was scrubbed from many a town square after the country's reunification under democracy and capitalism in 1990.