In Toronto, where an estimated 350,000 joined a demonstration, participants told BBC Persian they were there to speak out on behalf of friends and family inside Iran.
Street protests broke out in Iran on 28 December, initially sparked by economic turmoil and fuelled by long-running discontent with the country’s leaders.
Demonstrations spread to more than 100 cities and towns across all of Iran’s provinces.
The US-based Human Rights Activists News Agency (HRANA) has confirmed the deaths of 6,872 protesters, including more than 150 children.
Iranian authorities have acknowledged that at least 3,000 people were killed, but have claimed some were members of the country’s security forces.
Many demonstrators in Iran have chanted Pahlavi’s name and called for his return to political leadership.
Groomed from birth to inherit the throne, Pahlavi was 18 years old when the 1979 Islamic revolution swept away his father’s monarchy.
Almost 50 years later, Pahlavi is once again seeking to shape his country’s future.
But critics question whether his vision for Iran would ultimately lead to a democracy.