Each year the Big Give project teams up with charities, philanthropists and the public to raise money for good causes. For one week only starting on November 29, donations to Theatr Clwyd will be doubled through match funding.
Theatr Clwyd will be raising funds towards the major redevelopment work.
A spokesperson for the theatre said: "The project will ensure Theatr Clwyd remains open and can be enjoyed for generations to come.
"A survey in 2010 found the building was nearing the end of its life but the project will transform the building making it fully accessible with world class theatre on its stages and community at its heart.
"With a youth hub, dedicated arts and health suite, sensory garden, village shop and indoor and outdoor play areas, Theatr Clwyd will become a destination to enjoy art, meet friends, have respite, learn a new skill and most importantly have fun."
"During The Big Give Week a £10 donation becomes £20 to support your world class theatre in the heart of your community."
The project has been part funded by Welsh Government, Flintshire County Council and Arts Council of Wales
It has a fundraising target of £5 million and so far £3.2 million has been raised including £1.5 million from Moondance Foundation, the largest single donation for an arts organisation in Wales.
Match funding has been provided by supporters of Theatr Clwyd and The Reed Foundation.