Sporting were already assured of a second-placed finish prior to Saturday's game, while Nacional's position of fifth was also in no danger.
However, the hosts appeared hungry for an upset at Estadio da Madeira and were able to claim a point as Sporting failed to win for only the second time in 11 games.
Nacional suffered a setback when Nuno Campos found his own net six minutes before the break.
Islam Slimani could have doubled Sporting's advantage shortly before the hour mark when he scooped over the crossbar, and Nacional made him pay in the 76th minute.
Reginaldo drilled the ball across goal after a previous shot had rebounded off the left-hand post, and Diego Barcellos was on hand to make the telling touch.
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