The supermarket, along with Noman Collett, BASF and Hadlow College, is a main sponsor of the annual event - which takes place on 15-16 October in Kent.
It has sponsored the show since 2004 but is now expected to pull out in 2009.
A representative for Tesco denied that the re-evaluation of its involvement in the show was a cost-cutting exercise. She said: "Tesco sponsors a number of events as well as supporting our charity of the year, which this year is Marie Curie Cancer Care. We receive thousands of requests each year ... In order to be fair to all those who ask, we try to vary the events we support so that more occasions can benefit."
National Fruit Show chairman Jeremy Scott told Grower that he is disappointed with Tesco's decision but hopes that other supermarkets will look to invest in future.
"For a number of years we've been trying to get other supermarkets such as Waitrose and Morrisons on board."
Vice-chairman of the show Robert Oliver added: "(Tesco) has been a very good sponsor to us in the past but all good things come to an end. Hopefully we shall find another sponsor for next year to carry us through.
"In the past, we have had people in the wings who would like to sponsor us so it's a case of approaching them and finding out whether they still wish to.