The Blues travelled to Lonsdale Oval to meet the Lions, part of a bunched top six contingent.
Accuracy proved the difference in the first term, as Tonny missed two opportunities to post the opening goal before eventually getting on the board late in the term.
Contrastingly to the Blues’ 1.3, Mulwala kicked 3.1 to take a 10-point advantage into the first break.
Tongala fought back in the second with a pair of quick-fire Jack Hammond goals getting his side to the lead and a battling quarter ended with the teams locked at 33 at the half.
The Blues jumped back to the lead with the first major after the break, but the visitors let their levels slip later in the third, and the Lions reeled off three consecutive goals to hold a tenuous 11-point lead at the final change.
Tonny twice fought within a goal in the last term, but Mulwala responded on each occasion, securing a 10.5 (65) to 8.5 (53) victory.
Hammond finished with three majors to lead Tongala, while Kyle Fitzgerald and Darcy Laffy added two each.
The Blues couldn’t find an answer for Beau Seymour, who capitalised on good service to kick five.
Tongala (5-6) still sits a game back from sixth spot after Moama’s bye and is now two games adrift of a cluster of four sides between second and fifth.
Another important clash looms as the Blues prepare to host one of those four sides and the defending premier Cobram at Tongala Recreation Reserve this Saturday.