Chris Shields’ goal two minutes into the second half proved the difference between the sides on the night, with the Lilywhites advancing to the final on Saturday May 10th with a 3-1 aggregate lead having beaten Trevor Croly’s side 2-1 in Tallaght three weeks earlier.
Dundalk had the better of the chances throughout but did have to defend resolutely at times to keep the Hoops out.
The home side’s best opening of the first half came on the half hour mark when Andy Boyle headed a corner over. Five minutes before the break through, Peter Cherrie had to be at his best to keep a deflected shot from Ronan Finn out.
The breakthrough finally arrived two minutes after the restart when Shields met Ruaidhrí Higgins’ free at the back post to prod it home past Craig Hyland.
Both sides had their chances after that with John Mountney bringing a fine low save out of Hyland before Karl Sheppard blazed over from close range.
Rovers kept pressing until the end but never really troubled Cherrie as Stephen Kenny’s side held out to book the club only their second ever Setanta Cup final appearance.
The venue for the May 10th final will be decided on Thursday while the fixture means that Dundalk’s scheduled league clash at home to neighbours Drogheda Utd on May 9th will have to be arranged.
Dundalk: Cherrie; Gannon, Boyle, Rossiter, Massey; Shields, Higgins; Mountney, Towell (O’Donnell 88), Horgan (Meenan 77); McMillan (Hoban 70).
Shamrock Rovers: Hyland; Cornwall, Heaney (Kehoe 76), Kenna, Byrne; Finn (Kilduff 76), Robinson, Bayly, Waters (Brennan 69); Zayed, Sheppard.
Referee: Raymond Crangle.