Muslim Youth Focus Group organised the event to voice concerns about issues such as radicalisation.
The event was held as it emerged four teenage girls who were barred from travelling abroad were from the same school attended by three girls already thought to have fled to Syria.
All seven attend Bethnal Green Academy in Tower Hamlets.
The name of the school was revealed after reporters argued it was in the public interest.
The event was aimed at young British Muslims to help create a platform for them to discuss issues such as Islamophobia, Islamic State and the war in Syria.
In mid-February, police raised concerns following the disappearance of Kadiza Sultana, 16, Shamima Begum, 15, and Amira Abase, 15, from their homes in east London.
Shamima used the passport of her 17-year-old sister to leave the UK, police have said.
Young people, police, teachers, faith leaders and Muslims from the world of entertainment gathered at the Muslim Youth Festival to explore views on what it means to be a Muslim today.
Role models spoke at the event including music star Naughty Boy, whose real name is Shahid Khan, and has been working with Zayn Malik, who recently announced he was leaving One Direction.
Imam, Dr Mohammed Fahim of South Woodford Mosque said: "Young British Muslims, irrespective of their ethnicities or gender, should feel proud to live in a country like Britain which respects human rights and gives them equal opportunities and permits them to practice their religion without any fear or oppression."
Hundreds of young British Muslims have attended a festival in London on how to divert people away from extremism.