Goals from Sam Surridge and Hany Mukhtar ensured Nashville will head into the MLS postseason as the top seed after dominating the Eastern Conference.
The Supporters' Shield is awarded each year to the MLS team with the best record over the course of the regular season.
"When we started out in January, we put our minds to trying to accomplish big things with the club," Nashville head coach B.J. Callaghan said after the win.
"The Shield for us is symbolic of our body of work throughout the year -- being really really consistent, and we'll enjoy it tonight," Callaghan added.
Nashville will now have home-field advantage throughout the playoffs, including the December 18 MLS Cup final.
Nashville lead the Eastern Conference with 71 points from 31 games, 16 points clear of Lionel Messi's Inter Miami in second place.
Miami, with Messi starting on the substitutes bench after a midweek trip to Spain to receive a humanitarian award, were beaten 2-0 by New York Red Bulls on Saturday.
Messi appeared in the second half but was unable to inspire a comeback for the Florida club.