Harlequins showed remarkable composure to maintain their patience in a contest that stretched to an exhausting 100 minutes and was always intensely disputed.
NICS showed typical Ulster doggedness as they gave Harlequins the most intensive examination and went close to an upset win.
Twice NICS led and their relentless application and capacity for hard work meant they were vulnerable for a brief period at the start of the second half.
It was only in the shoot-out, when Harlequins converted four of their five penalties, that the favourites succeeded in illustrating their superiority.
It seemed bizarre for Harlequins to include in their selected five shooters, a player who had not taken any part in the match. And it did not come as a surprise when NICS goalkeeper, Alan Godden saved Philip O'Driscoll's shot.
Harlequins were assured and efficient as Paul Lombard, Sean Nicholson, John Hobbs and David Eakins converted penalties to edge into the final.
Eakins had converted another penalty stroke early in the second half to equalise Jesse Bonjer's first half goal for NICS. After the skilful Aaron Gill had restored NICS' lead in the 50th minute, it was Jason Black who claimed Harlequins' second equaliser following a short corner.
Harlequins struck a peak early in the second half when they moved the ball at pace and with accuracy but they allowed NICS to slow the game and were guilty of over-playing the ball to their detriment.
They had reason to be grateful for the outstanding goalkeeping of Wesley Bateman and the devastating technique of Eakins' strokes from set pieces.
The latter reflected the general mood when he said: "Relief, that is what I'm feeling. They gave us a big shock really. We knew they were going to be physically tough but I was very surprised by how well they actually played."
Coach Stephen Dale said: "Both sides were cagey. We played well ... how can I put it ... steady hockey. Nerves played a part, there were a lot of nerves out there, a lot of nerves.
"We would love to play a little bit more flowing, a little bit more going forward. A lot of it was nerves, don't ask my why? Please God for the final we'll try and get those out of the way."
Team captain Jason Black pinpointed two obvious points of difference between the teams. "Wes (goalkeeper Bateman) pulled off a couple of brilliant saves in the strokes and that was critical.
"Eakins is really catching hold of the flicks now, he takes them with such confidence you know he can put it anywhere.
"It was a very tight match and we have left games like that behind us before so it is brilliant to have come out on top."
: A. Godden; D. Symington, C. Maskery, J. Anderson, R. Cowden; P. Johnston, A. Johnston, G. Grundie, C. Posnett; A. Gill, C. Irwin. Subs used: G. Gray.
: W. Bateman; S. Nicholson, P. Chambers, J. Hobbs, J. Black; P. Lombard, J. Aherne, M. Black; D. Eakins, D. Lombard, D. Egner. Subs used: E. Gash, L. d'Alton.
: C. Porter and D. Stewart.