Mourners will gather at the Auld Kirk in Ayr to say a final farewell to the 77-year-old, who died last weekend.
The entertainer was said to have suffered a stroke last month and was being treated in the Ayrshire Hospice, Ayr.
He died peacefully with his family around him, a spokeswoman at the hospice said.
Mr Alexander was one half of the Alexander Brothers with his sibling Tom.
The brothers, originally from Cambusnethan in Wishaw, Lanarkshire, were among Scotland’s best-loved entertainers and performed for more than 50 years.
In the 1950s they started performing on stage in a series of talent contests across central Scotland with Jack playing the piano and Tom on the accordion.
They won every competition they entered between 1950 and 1956, according to their fan club biography, and started playing professionally in 1958.
They recorded more than 30 albums, the first titled Highland Fling, and toured Canada, the United States, Australia and New Zealand.
Both brothers were awarded MBEs for services to entertainment in the 2005 New Year Honours List.