Team Melli lost to the South American giant 3-2 (25-20, 25-23, 24-26, 20-25, 15-10) in Pool B in Chicago.
Milad Ebadipour had 22 points for Iran, while Ricardo Lucarelli Souza led Brazil with 16 points.
Iran, who was defeated against Poland 3-1 in its first match, came fifth in the 2019 Volleyball Nations League (VNL).