The vigils were hosted by Physicians for Human Rights (PHR), a co-recipient of the 1997 Nobel Peace Prize, as well as friends and colleagues of the brothers. Vigils were held in such far-flung locations as Kabul and Rome, Bangkok and Buenos Aires, and Nairobi and New York City.
Participants demanded the release of the doctors, saying that "treating AIDS is not a crime."
The brothers were found guilty of being involved in a U.S. plot to overthrow the Iranian government. Arash was sentenced to six years in jail, while Kamiar was sentenced to three years.
In an interview with RFE/RL's Radio Farda, Sarah Kalloch, outreach director at PHR, said, "We are hopeful that Iran would show the same Islamic kindness that they have shown in the case of Iranian-American journalist Roxana Saberi, who was facing the same charges as the Alaei brothers."
Saberi was released from a Tehran prison on May 11.
According to PHR, more than 5,000 people from 130 countries have so far signed an online petition demanding the release of the Alaei brothers.