After trailing by 10 points with 25 minutes on the clock, the north Cork side battled back to parity by full-time and took the spoils by dominating the extra 20 minutes.
Led by their talisman Jamie Coughlan (1-8 from placed balls), the Avondhu side clawed their way back into the game thanks to a brilliant final spell that just blew away the divisional side.
Corner forward Tim O’Mahony also showed his undoubted class on the night, bagging a vital 2-3 from play, with his two goals killing off the tie at the death.
Others to impress for the men in green and gold were Diarmuid Buckley at left full-forward (1-2), centre back Conor Twomey and midfielder Eric O’Connor, with Buckley showing plenty of skill and pace throughout.
For Duhallow this was a disappointing end, after an amazing start that saw them race into a 2-11 to 1-2 lead by the 22nd minute, and they turned leading by 2-11 to 1-5 at half-time.
First-half goals from Donal Hannon and Barry O’Connor looked to have set the divisional side on their way to the last four, with Kanturk’s Ian Walsh and Meelin’s Jason O’Callaghan adding another six points between them as Duhallow looked unstoppable early on.
Shandrum trailed their opponents for 59 of the 60 minutes and only took the lead for the first time in extra-time — with points from O’Mahony levelling things up on 59 minutes, and then putting his side in front on 63.
Once Shandrum got themselves in front, there was only going to be one winner as the Duhallow side seemed to know the game was up.
Next up for Shandrum is a last four clash with Carrigaline next Saturday.
Scorers for Shandrum: J Coughlan 1-8 (1-0 pen, eight frees); T O’Mahony 2-3; D Buckley 1-2; J Lane 0-2; K Cagney, JP Maloney, C Twomey, S Griffin, P Hassett 0-1 each.
Duhallow: D Hannon 1-5 (three frees); I Walsh 0-4; B O’Connor 1-0; J O’Callaghan, L O’Keeffe 0-2 each; L O’Neill, J Fitzpatrick, D Kenneally 0-1 each
SHANDRUM: E Maloney; B Naughton, D Browne, M Curtin; E O’Connor, C Twomey, B Morrissey; S Griffin, P Hassett; JP Maloney, M Maguire, J Coughlan; T O’Mahony, K Cagney, D Buckley. Subs: J Lane for S Griffin (27), S Griffin for M Maguire (65), D Geary for JP Maloney (75).
DUHALLOW: D Kearney (Lismire); P Allen (Newmarket), R O’Connor (Banteer), K Cremin (Dromtarriffe); G Forde (Newmarket), L O’Neill (Kanturk), M O’Gorman (Dromtarriffe); D Hannon (Newmarket), J O’Callaghan (Meelin); J Fitzpatrick (Kanturk), D Kenneally (Kanturk), G Linehan (Kilbrin); C Murphy (Castlemagner), I Walsh (Kanturk), B O’Connor (Newmarket). Subs: S Crowley for C Murphy (ht); L O’Keeffe (Kanturk) for I Walsh (41), I Walsh for B O’Connor (55), N Field (Kilbrin) for D Kenneally (67).
Referee: C Lyons (Nemo Rangers)