Banging drums and chanting for regime change, the giant and boisterous rally in Munich was part of what Pahlavi described as a "global day of action" to support Iranians in the wake of deadly nationwide protests.
He also called for demonstrations in Los Angeles and Toronto. Police said in a post on X that the number of protesters reached some 250,000, more than the organisers had expected.
"Change, change, regime change" the huge crowd chanted, waving green-white-and-red flags with lion and sun emblems. Iran used that flag before its 1979 Islamic Revolution that toppled the Pahlavi dynasty.
At a news conference, Pahlavi warned of more deaths in Iran if "democracies stand by and watch" following Iran's deadly crackdown on protesters last month.
"We gather at an hour of profound peril to ask: Will the world stand with the people of Iran?" he asked. He added that the survival of Iran's government "sends a clear signal to every bully: kill enough people and you stay in power."
At the Munich rally, demonstrators sported "Make Iran Great Again" red caps, mimicking the MAGA caps worn by US President Donald Trump 's supporters.
Among those sporting the caps was US Senator Lindsey Graham, a Republican from South Carolina who gave a speech to the crowd during which he was photographed holding up the headwear.
Many at the rally waved placards showing Pahlavi, some that called him a king. The son of Iran's deposed shah has been in exile for nearly 50 years but is trying to position himself as a player in Iran's future.
The crowd chanted "Pahlavi for Iran," and "democracy for Iran" as drums and cymbals sounded.
"We have huge hopes and (are) looking forward that the regime is going to change hopefully," said Daniyal Mohtashamian, who travelled from Switzerland, to speak for protesters inside Iran who faced repression.
"There is an internet blackout, and their voices are not going outside of Iran," he said.
About 500 protesters also rallied outside the presidential palace in Nicosia, Cyprus, with many holding up banners with slogans against Iran's government and in favour of Pahlavi.
The US-based Human Rights Activists News Agency says at least 7005 people were killed in last month's protests, including 214 government forces.
It has been accurate in counting deaths during previous rounds of unrest in Iran and relies on a network of activists inside Iran to verify deaths.
Iran's government offered its only death toll on January 21, saying 3,117 people were killed. Iran's theocracy in the past has undercounted or not reported fatalities from past unrest.
Iranian leaders are facing renewed pressure from Trump, who has threatened US military action.
Trump wants Iran to further scale back its nuclear program. He suggested Friday that regime change in Iran "would be the best thing that could happen".
