Tauranga Sports had an Aifai Esera try - inexplicably unconverted from close range by Paul Morris - and a Nic Evemy candidate for try of the season to show for plenty of endeavour in the first half.
Evemy's try, featuring a grubber and two gorgeous wrap-arounds from Lewis Hancock and Byron McGuigan, looked to have blown the match open.
However, Whakarewarewa pivot Te Rangi Fraser grabbed the game by the scruff of the neck.
He made back-foot ball look like front-foot ball, and went through Sports seemingly every time the outside backs flew up out wide.
One foray late in the half swung the contest for good. A clean break down the right for Whaka ended with a chip kick and a try to Jason Harvey.
The second half began poorly with a yellow card to fullback Whaimotu Craft-Chemis, but No8 Siegfried Fisiihoi flourished in his absence.
The willing ball runner rumbled over from more than 20m out to help level the scores and smashed into everything in a final 40 minutes in which Sports barely fired a shot.
Raking Fraser punts were left to bounce, kick-offs were dropped and balls were kicked out on the full by a home side incapable of holding back the red and black tide.
For all of that, Sports had a chance to steal it late when a clever Brent Hamlin box kick produced a try in the corner for McGuigan. Morris missed to the right from the touchline .
Mount Maunganui defeated Te Puke 35-20 in the other semifinal.
Tauranga Sports 17 (Aifai Esera, Nic Evemy, Byron McGuigan tries; Paul Morris con) lost to Whakarewarewa 18 (Jason Harvey, Siegfried Fisiihoi tries; Te Rangi Fraser 2 pens, con).