The Take That singer and songwriter will now perform a fifth night of A Different Stage at New Theatre Royal on Monday, November 7.
His previously announced run of four nights at the venue, from November 8-11, sold out rapidly after being announced in April.
Many of the other nights on the 24-date tour have already sold out. More new dates are also announced today for Truro, Aylesbury and London.
Created by Gary and his long-time friend and collaborator Tim Firth, A Different Stage sees Gary narrate the journey of his life alongside the music from his discography.
One of Britain’s most successful songwriters and record producers, as part of Take That, he has won eight Brit Awards and sold more than 45m records.
In more recent years, Gary has also turned his attention to the world of theatre, working on hit shows Finding Neverland, Calendar Girls The Musical and The Band.
A statement on the venue’s website warns: ‘Ticket resales are not permitted for this event. Maximum four tickets per household.
‘The lead ticket booker must be in attendance and photo ID may be required on entry to the venue.
‘If you see or are offered tickets for sale online or on social media these tickets will not be valid at the venue on the day of the show.’