The club, based in Horsham, provides support to over 50 stroke survivors every week across West Sussex.
Over £325,000 was raised to pay for the building and landscaping work.
The extension means more members can join, particularly stroke survivors in wheelchairs. There is a therapy room where members can receive treatment in the privacy of a dedicated area as well as a new landscaped garden area.
Here is a selection of pictures by our photographer Steve Robards from the opening.
And you can read more from the ceremony, including the thoughts of Chris Tarrant, here.