Hundreds are expected to join in festivities in and around Armley Town Street after community group All Together Armley organised the first festival to be held in the town for many years.
Mr Bennett, who was born in Armley on May 9 1934, wrote to All Together Armley after hearing of the festival plans.
He wrote: “I’m afraid I don’t have e-mail or Facebook so snail mail will have to do.
“I send all good wishes for the Armley Festival which was a good place to grow up 80 years ago and I hope it still is. I could go to the spot on Armley Moor when I was told (aged six) that there was no Santa Claus and can remember walking from our home in the Hallidays to infants school in Theaker Lane three weeks or so after the war started in 1939.
“Good luck to you all and I hope it’s a great festival.”
Gudruhn Shemlit, chair of All Together Armley, said: “We were delighted to receive this letter of support from Alan Bennett, one of our favourite sons of Armley.
“It’s lovely to hear about his fond memories of living in Armley, but we think he may have been misinformed about Santa Claus.”
The festival will take place on Armley Town Street and Armley Moor between midday and 4pm tomorrow.
The free event will feature 52 different stalls representing an array of local businesses, organisations and charities.
Armley Moor will be hosting a funfair and visitors are being told to expect a special guest.