It is the first time they have been recognised at national level since 2012, when they won Silver.
Cranbrook also won a Silver Gilt medal in the Small Town category at the awards ceremony, which was held in Belfast.
Tunbridge Wells had already secured the Gold award for the South and South-East regional competition, an accolade which they have achieved for the past seven years.
David Elliott, Chairman of Royal Tunbridge Wells in Bloom, said: “I am thrilled to bits that Tunbridge Wells won a Silver Gilt at the Britain In Bloom Award ceremony. Thank you so much to the parks team and all our volunteers for their efforts.”
Helen Timms, Parks and Sports Team Administrator for Tunbridge Wells Borough Council, said: “We are extremely pleased to received the Silver Gilt award this year, and couldn’t have achieved this without the hard work and dedication of all of our volunteers, supporters and sponsors.
“We received positive and very constructive feedback from the judges, which we will use this coming year to improve our entry.
“One of our national judges judged us previously in 2013 and commented that he could see a vast improvement in our achievements.”
The Assembly Hall Theatre is currently displaying an exhibition of images taken to reflect this year’s entries in the town’s own competition.
Local photographers sent in their pictures of floral displays in the town, its parks and across the borough, and the results are featured in the show, which is called ‘Blooming Marvellous’.
Royal Tunbridge Wells in Bloom is a horticultural campaign run by a committee of volunteers with support from Tunbridge Wells Borough Council and the Kent High Weald Partnership.
This year the competition featured a record number of 285 entries, and more than 70 photographs were submitted between July and August; 23 images have been chosen for the exhibition.
Marketing officer Katharina Mahler-Bech said: “Royal Tunbridge Wells in Bloom and the Assembly Hall Theatre would like to thank everyone who participated in the competition and submitted photographs. It was incredibly hard to choose which pictures to include.”
For more information about the competition, visit royaltunbridgewellsinbloom.org.uk Twitter: @RTWinBloom and Facebook: @RoyalTunbridgeWellsinBloom