Away at Scott Oval in Cobram, the Blues never really got into the contest, falling behind early and struggling to generate opportunities at goal throughout.
Tongala could find only 23 combined points over the first, second and fourth quarters, the third period the only bright spot.
Tonny had some early hope after kicking the first of the game, but the Purples reeled off three straight to take a 2-8 lead into the first break.
Nathalia continued to roll into the second, and after the sides traded the first two goals, another four in a row put the Purples in complete control at half-time, leading 55-15.
The Blues showed the signs that they could match it with Nathalia in the second, trading effectively and narrowly winning the quarter 25-20, but remained in a four goals hole headed into the last.
The good times didn’t continue in the last, and the Purples resumed their domination, rolling to a 15.12 (102) to 7.6 (48).
Tom Holman was the only attacking spark for Tongala, kicking six of his side’s seven majors, while Liam Evans was the crux of the Purples’ attack with seven.
Nathalia goes on to battle Cobram in the preliminary final, after the Tigers fell to Congupna by five points in the qualifying semi-final.
The Blues will now look to regroup after returning to finals after a few years away in their first year under returning coach Jordan Souter.
The game
Tongala: 1.2, 2.3, 6.4, 7.6 (48)
Nathalia: 3.2, 8.7, 11.10, 15.12 (102)
Goals
Tongala: Tom Holman 6, Mackenzie Cowley
Nathalia: Liam Evans 7, Clancy Congues 2, Harry McDonald 2, Joshua Dohnt, Gus Frostick, Campbell Mann, Jonty Mann
Best
Tongala: Beau Joyce, Tom Holman, Levi Taylor, Bailey Waasdorp, Kyle Fitzgerald, Mitchell Fitzgerald
Nathalia: Logan Campbell, Kai Lundberg, Liam Evans, Jack Duggan, Harry McDonald, Ned Frostick