The singer planned two concerts at his former school Orangefield High in east Belfast for 22 and 23 August, with one show specifically for ex-pupils and staff.
But due to huge demand for this performance, Morrison will now go forward with a third gig for ex-staff and pupils on 24 August with tickets available from Saturday 19 July between 1-3pm.
Also featuring during this year's EastSide Arts Festival will be a host of performances, visual art, lectures, walking tours, film and music, which will include the playwright Marie Jones, writer Brian Keenan, Thin Lizzy musician Eric Bell, poet Gerald Dawe and actor Sam McCready.
The programme boasts a range of east Belfast talent, including singer Kaz Hawkins, novelist Glenn Patterson, actor Dan Gordon, and the late writer and broadcaster Sam Hanna Bell.
Continuing on the cross community theme the festival will also feature a performance, in partnership with west Belfast's Feile An Phobail, of RMS Titanic - An Evening with Donal Lunny, Anthony Cronin, and guests.
We hope to welcome as many people from the east of the city and beyond during the festival and hope that they leave with a sense that the arts is growing and thriving here.
Maurice Kinead, CEO of East Belfast Partnership
Maurice Kinead, CEO of East Belfast Partnership, said: "This is the 3rd annual festival we have delivered and we believe, yet again, that we have created a programme that will reach out to everyone in the East Belfast Community and beyond.
"With the closure of Orangefield School we felt it was important to celebrate its legacy and showcase the huge talent that emerged from the school. We are immensely proud that some of the successful, creative and high profile past pupils are returning to mark this momentous occasion with us.
Roísín McDonough, Chief Executive, Arts Council of Northern Ireland, added:"Across this great city the arts have been a marvellous tool for building identity and developing community, transforming and sharing the space in which we live, in new and inspirational ways.
"I welcome this year's varied programme of arts events - there is something for everyone, from young to old and everyone in between.The EastSide Arts Festival will play a pivotal role in the life of east Belfast this year and in years to come and I encourage everyone to get involved."
The EastSide Arts Festival runs from 21-25 August.