The reunited band burst onto the music scene in 1987 with hits like Sweet Little Mystery and Wishing I Was Lucky.
The Clydebank outfit have joined Emeli Sande, Olly Murs and Deacon Blue in the line-up of outdoor shows at the venue in July.
The band, who notched up number one singles with With a Little Help From My Friends, Goodnight Girl and Love Is All Around, have sold more than 15 million records.
The group split up in 1997 but have been performing regularly since 2004, including a memorable appearance at the Live 8 concert at Murrayfield in 2005. This summer's show is billed as a 30th anniversary celebration of their debut album, Popped In Souled Out.
Frontman Marti Pellow said: “It was a major career highlight when we took to the stage at Edinburgh Castle some 25 years ago. We’re honoured to be asked back and it is sure to be special.”
Guitarist Graeme Clark added: “We’re coming back to to celebrate the 30th anniversary of our Popped In Souled Out album and to do it on this scale at Edinburgh Castle is incredible.”
Mark Mackie, director of the Castle Concerts series, said: “It is with great delight we are able to announce today that pop sensations Wet Wet Wet will be the fourth act to play Edinburgh Castle this July.
“Its only taken us 25 years to get the band to come back and play this truly unique venue.
“Over the years, the castle has played host to many international stars such as Rod Stewart, Blondie, Elton John, The Proclaimers, Leonard Cohen, Stereophonics, Sir Tom Jones and Pink.”
Nick Finnigan, exective manager of Edinburgh Castle, said: “Wet Wet Wet are one of the most successful Scottish acts of the last 30 years, so it’s exciting to have them as part of our forthcoming Castle Concerts Programme.
“We’re all looking forward to welcoming the band back to Edinburgh Castle for what’s sure to be a wonderful show.”
Tickets for the Wet Wet Wet show at Edinburgh Castle on 15 July go on sale this Friday.