After coming off the bench to score a dramatic winner in his debut on Friday night, the World Cup champion from Argentina wasted no time in his first start with the MLS side.
The new captain received a lovely lofting pass from former Barcelona teammate Sergio Busquets and, after initially hitting the post, fired home his own rebound to put Miami up in the eighth minute to roars of approval from the home crowd.
Messi slotted home a second in the 22nd minute, turning in a driven cross from team-mate Robert Taylor, who notched a brace of his own on a hot night in Miami.
After scoring, Messi stopped and pointed from the field at the team co-owner David Beckham, who was watching the game. The gesture was met with a wide smile from the former Manchester United great who helped lure Messi to the MLS despite a massive counteroffer from Saudi Arabia.
Atlanta's best chance at getting on the scoreboard came with a late penalty kick from Thiago Almada but Miami keeper Drake Callender read it perfectly to preserve the clean sheet.
Messi and fellow Argentinian Almada hugged when Messi was subbed out in the 78th minute and the pair exchanged shirts after the match.
With the win, Miami have now won their group in the Leagues Cup tournament, which is a World Cup-style tournament featuring all teams from MLS and Mexico's Liga MX.
