Watsonians beat Edinburgh Accies in the quarters and then Jed-Forest in the semi-final with tries from Mark Bertram, Euan Miller and Reiss Cullen in a 19-7 win.
For their part, Hawick showed title potential with a 24-21 win over an all-Fijian British Army side before defeating Gala 21-14 in the second of the semis.
In the final, Hawick struck first with a try by scrum half Sean Goodfellow converted by Lee Armstrong. A try by Bertram, converted by Jack Ferguson, brought Watsonians into the fray. Before half-time, however, Armstrong crossed to put Hawick into a 12-7 half time lead.
Hawick went further ahead through tries by Ross Graham and Craig Russell, the latter converted. That triggered tries by Watsonians’ Andrew Chalmers and Cullen but not enough to stop Hawick.