The Perth Theatre, a B-listed Edwardian auditorium, will be restored to its former glory and a new 200-seater studio theatre created at the venue when it reopens at the end of 2017.
Bosses at the trust behind the project have launched a fundraising push to raise the final £1.5 million to get work underway by the end of the year, once planning permission is secured.
The long-awaited revamp has already been in the planning staged for more than eight years and the venue was closed down at the beginning of last year to make way for the revamp.
However a review overseen by the theatre’s new chief executive, Gwilym Gibbons, saw the budget soaring by £2 million and a number of changes to the designs.
The project - which involves the creation of new education, workshop and rehearsal spaces - has been pledged £15 million by a range of funders, including Perth and Kinross Council, Creative Scotland, and the Heritage Lottery Fund.
The refurbishment has won the backing of Perthshire-born Star Wars actor Ewan McGregor, who said his “life changed” when he was offered a job as a stagehand after quitting school.
Earlier this year, he said: “ It was the best thing that happened to me. It set me on my way.”
A spokeswoman for Horsecross, the trust which runs the theatre and Perth Concert Hall, said: “Perth Theatre has a long history of artistic innovation and excellence having been at the heart of cultural life in Perth for over a century.
“The transformation of the theatre will restore and redevelop one of Scotland’s oldest and best loved theatres for generations to come.”