New seating and ventilation for the auditorium, better technical facilities and a refurbished studio space are planned for Bristol's Old Vic.
The Bristol Old Vic is appealing for money from the public and businesses
Now £2m needs to be raised to complete the work at the 240-year-old theatre.
Appeal chairman Nick Bacon asked for donations to help safeguard the Old Vic's future, urging Bristolians to help save the "gem of a theatre".
Details of the £7m refurbishment for the historic attraction were announced on Tuesday.
The new seating would offer extra leg-room and be positioned to avoid the majority of the theatre's Georgian pillars.
Audiences would still enter the building through the King Street entrance, although the front of house area is due to have a repositioned box office, refurbished foyers and cafés.
The disabled toilets would be moved from backstage to front of house to make them more accessible.
Under the plans, an education space would also be built in what is currently the basement adjacent to the studio.
The Old Vic has already received pledges of over £5m from a range of donors including Arts Council England, Bristol City Council and various trusts, including £1m from the Sainsbury Family Charitable Trusts.
Corporate donations ranging from £5,000 to £100,000 have also been pledged.
It is hoped the project will be completed by December 2008.