Selkirk edge Kings title favourites to win Langholm Sevens
Selkirk were in the driving seat at the break, but despite losing Reiss Cullen to a yellow card, Watsonians fought back to leave Selkirk defending well to take the cup.
Selkirk raced into an impressive 24-7 half-time lead with tries by Darren Clapperton, Euan McDougall, Ciaran Whyte and Fraser Anderson to a Rory Drummond touchdown.
After the interval, Cullen and Ali Harris cut the deficit, but Selkirk hung on in the final minutes.
Watsonians beat Melrose in the first semi-final, Selkirk seeing off Jed-Forest.