Neath 32 Cardiff 10
Fly-half Lee Jarvis bagged 17 points to book Neath a place in the Celtic League final against Munster at the Millennium Stadium on February 1st.
Jarvis scored one of Neath's four tries, kicked three conversions and two penalties as the power of the Welsh All Blacks proved decisive in an entertaining all-Welsh clash at The Gnoll.
Both sides had carved out impressive victories on their travels in the quarter-finals - Neath at Pontypridd and Cardiff at Edinburgh. However, there never appeared any danger of an away triumph at The Gnoll during a one-sided first half.
Almost for the whole of the opening 40 minutes Cardiff were pinned back in their own half, struggling to break free from the firm grip Neath had on the game.
With the home pack dominating the line-out and causing Cardiff's scrum all sorts of problems, the capital club were unable to give their international three-quarters enough quality possession to trouble Neath.
After a period of sustained pressure on the Cardiff line it was Jarvis who opened the scoring with a 15th minute penalty. Then with the Cardiff scrum creaking number eight Nathan Bonner-Evans drove over from close range for the game's opening try.
With Neath continuing to test the Cardiff defence it was Tongan centre Dave Tiueti who crossed after a clever midfield switch to take the home side into a convincing 17-0 interval lead.
Cardiff were offered some hope three minutes after the restart with a try by scrum-half Richard Smith.
Fly-half Iestyn Harris then added a penalty to his earlier conversion to make it 17-10 and give Cardiff renewed hope of a comeback, similar to the one that earned them the win in Edinburgh.
But a moment of magic by Jarvis, dummying a dropped-goal attempt then racing over, put Neath back in control.
The number 10 added another penalty, before wing Gareth Morris raced over late on to seal Neath's place in next month's showpiece final.