KCB won a penalty shoot-out at Moi Stadium to wreck favourites Western Stima hopes of sailing to the GOtv semifinals.
The Bankers reached the showpiece for the first time in many years but Western Stima coach Henry Omino will be left fuming at his players for failing to utilize open chances aganist second tier side.
Brian Marita missed an open chance in the 14 minute with Keneth Otieno also missing a seater in 70th minute after being put through by Kennedy Miguna to hit the side net, and Stima disappointment will be felt more acutely after they cracked under the pressure of the spot-kick shoot-out.
John Odhiambo missed KCB first penalty, but Stimas Fredrick Shimonyo and Job Omuse missing first two efforts to get an advantage.
Deniss Ngaga,Frank Balala and Juma Mpogo were then on target for KCB, with Kenedy Otieno and Wesley Onguso,Bernard Ondieki responding for Western Stima.
And with KCB fans providing a deafening backdrop of expectation, Gabriel Ondiek missed decisive penalty for Stima to send one half of Moi Stadium freezy.
KCB coach Leonard Saleh looked close to tears as players bench raced on to the turf to celebrate their historical win..
For Western Stima coach Henry Omino, there was only disappointment and they must now turn their attentions back to the pursuit of the Kenya Premier League title.
As expected, Western Stima made no changes to the side that secured a Premier League victory on Sunday beating Nairobi City Stars by solitary goal.
Western Stima acquitted itself well in a drab first 45 minutes that offered little in the way of quality or chances.
Wesley Kemboi sent KCB custodian clear in a dangerous position inside the area in 5th minute , but headers has not been Western Stima Striker strong point and he headed well off target.
Brian Marita then shot wide for Stima before goalkeeper nearly gifted bankers an opener in the 24th minute, stumbling over an attempted clearance and almost allowing bankers striker in to score.
KCB had a narrow escape 20 minutes later when Wesley Kemboi shot was saved inches to the goal mouth after a deflection by custodian Juma Mpongo.
The bankers almost had an opening goal to cheer minutes after the break, but Garbiel Adika made a superb low save from Frank Balala 25-yard drive.
Western Stima starting XI: Gabriel Andika (GK), Dennis Sikhayi, Wesley Onguso, Maurice Ojwang, Joash Onyango, Frederick Shimonyo (C), Kenneth Muguna, Brian Marita, Frederick Nyarombo, Wesley Kemboi, Kennedy Otieno
Subs: Levis Opiyo (GK), Victor Oduor, Bernard Ondiek, Daniel Makachi, Kevin Okoth, Francis Ocholla, Estone Esiye