The Lingen Davies Cancer Fund are organising the big event, which is taking place at the Hamar Centre on the hospital site on Sunday 18 August, starting at 2pm.
All money raised will go towards improving facilities for local cancer patients in Shropshire and mid Wales through the funding of new buildings and equipment.
Louise Cliffe, Fundraising Manager for Lingen Davies, said: “It’s going to be a brilliant old-fashioned family fun day.
“It promises to be a fantastic afternoon where games, tombolas and raffles will be held. Refreshments, including tea, coffee and cakes, will be available. Admission is free and we have also arranged free parking for the day, so why not come along and join us?
“We’re hoping the sun will shine for us as it has over the last few days, but if it doesn’t we’ve got plans to move inside the Hamar Centre and continue the fun.”
Lingen Davies have been supporting cancer services in Shropshire and mid Wales for more than 30 years. Last year saw the opening of the state-of-the-art Lingen Davies Cancer Centre, with the charity contributing £3.2 million towards the £5 million total build cost.
More recently, the charity provided £107,000 to help upgrade Endoscopy facilities at the Princess Royal Hospital in Telford.
Lingen Davies is also encouraging the public to have their own garden parties in aid of the charity, inviting their family, friends and neighbours to come along.
Anyone interested in staging their own Garden Party this summer can contact the Appeals Office on 01743-492396 in order to get hold of posters, tickets and flyers to help promote the event.