A service was held in the US town of South Hadley -- three years after the Irish teenager took her own life at the age of 15.
Phoebe's death attracted huge international attention as it was the first high-profile case of a child taking their own life after being tormented by bullies. Speaking to the Herald from Massachusetts, Phoebe's aunt described the service as "extremely special".
Eileen O'Brien Moore said the family has been deeply saddened by the recent deaths of bullied teenagers Ciara Puglsey (12) and Erin Gallagher (13). "Phoebe would not have wanted other kids to join her in the place where she is.
"Although she had a short life, we hope her legacy will change things. She was an amazing young girl.
"We take comfort in the fact that her death has impacted on so many people across the world." Ms O'Brien Moore said the family had struggled to heal over the past years but the Mass really helped.
"We were so happy and touched to see so many people there. Hundreds of people turned out for the Mass. We are heartened and humbled by it," she said.
Local priest Fr Tom Shea held the Mass in Phoebe's memory after being contacted by her family.
She died at 15 after suffering a campaign of relentless bullying at the hands of students in her school.
Fr Shea agreed to stage the Mass despite being contacted by Phoebe's family less than two weeks ago.
Ms Moore spoke of the how her daughter and Phoebe's cousin, Molly (23), was determined that a Mass would be held.
"Molly phoned me and said, 'We need to have a Mass for Phoebe' and we are so grateful to the church that they agreed instantly," she said.
"Loads of people who cared about Phoebe turned out. The church was packed with people who were touched by her death."
Most of Phoebe's family, including her father Jeremy and little sister Lauren (16) are currently living in Fanore, Co Clare.
Jeremy Prince has been at the forefront of the campaign to tackle bullying in Irish schools and is a patron for the National Anti Bullying Coalition.
Phoebe Prince was found dead in her South Hadley home in January 2010 in after she was targeted for bullying by classmates including vicious social network comments.
Six teenagers stood trial accused of bullying Phoebe in the weeks and days before her death. Great focus was paid to two male students at South Hadley High -- Austin Renaud and Sean Mulveyhill -- with whom Phoebe had shared relationships.
Both were charged with statutory rape, charges which were later dropped.
Even after Phoebe's tragic death, bullies took to social networks, posting messages such as "done" and "she got what she deserved".