Jack Penate, Lethal Bizzle, The Maccabees, Erol Alkan and Matt And Kim have been added to the Underage Festival lineup.
The one-day event, reserved for 14-18 year olds, takes place at Victoria Park in east London on Friday 10 August.
Other acts confirmed include Pigeon Detectives, Rumble Strips, Cajun Dance Party, Pull Tiger Tail, Mumm-Ra, The Young Knives and The Maccabees.
The festival is inspired by the highly successful Underage club night and, in keeping with its spirit, tickets cost just £20.
Commenting on the inaugural Underage Festival, promoter Sam Killcoyne said: “It's just gonna be a massive version of the club over 3 stages. A days worth of undiluted fun and mayhem minus the adults. Bring your spacehoppers!!”