The group will top the bill on the Friday night as the town centre gets set to host its biggest ever live event in May 2022.
The organisers of Breakout still have more names to add to the line-up which will showcase some of the biggest bands from Scotland - and a host of local singer songwriters.
Breakout will run from May 27-29, turning Kirkcaldy’s waterfront into a live venue for the very first time.
Up to 30,000 music fans could descend on the town over the three days.
Wet Wet Wet will headline a Friday night bill which also includes Sandi Thom, Hue & Cry, and Callum Beattie - with one more act to be confirmed.
The weekend will also feature live sets from big names such as The Skids, Big Country, Goodbye Mr McKenzie, Midge Ure, Red Hot Chili Pipers, plus British reggae legends, Aswad.
Breakout’s main stage will be at the Basin car park, with a second dance and acoustic stage further along the Esplanade.
The festival will also feature some of the showmen from the Links Market.
The addition of Wet Wet Wet takes the festival a major step closure to completing its line-up.
The band enjoyed huge chart success in the 1980s and 1990s, reforming in 2004 and continuing after the departure of singer Marti Pellow in 2017.
It is set to unveil a new album, The Journey, their seventh as a band and their first with singer singer Kevin Simm.
It features a dozen tracks written and recorded during lockdown.
A spokesman for the promoters said: “We are delighted to add such a legendary band to our line up and can't wait to hear them belting out all their hits on Kirkcaldy Promenade.”
Breakout was originally scheduled to take place this month, but the decision was made to delay it until next summer after a spike in COVID cases.
The festival is designed as a fundraiser for the NHS as well as an opportunity for people to get back together again and enjoy live music after lockdown.
At the time, the promoters said: “As the event is in support of the NHS, we feel it would be irresponsible to run such a large event at this time.
"Your safety and enjoyment is of the utmost importance to us and while other festivals and events have introduced mandatory testing for attendance, we don’t feel it would be appropriate to introduce similar measures.”
The three-day event will give local performers a stage to showcase their music, and also mark the return of renowned Kirkcaldy DJ Graeme Park.
It will also spotlight a host of great Scottish talent with the line-up including leading Americana singer songwriter Dean Owens - who ghosted the Cash Back In Fife Festival before lockdown - The Rezillos, Colonel Mustard and The Dijon Five, and The Countess of Fife, fronted by punk legend Fay Fife.
Tickets for Breakout are on sale now. More details from https://www.skiddle.com/festivals/breakoutfestival/http://https://www.skiddle.com/festivals/breakoutfestival/