"We've reached 40 million fans here on Instagram. Thanks everyone!" wrote the Argentine national team on his account, leomessi, on Thursday.
On Instagram, Messi mainly posts family pictures, of his wife Antonella and his two children, while shying away from showing off his lifestyle.
On Facebook, the Barcelona star already has 84 million followers.
One of his most recent Instagram posts was made a couple of weeks ago to announce the launch of his new website, Messi.com.
However, Messi is still far from being the most followed Instagrammer since singer Selena Gomez is followed by 71.8 million.
Messi's rival, Portugal's Cristiano Ronaldo, also beats him with 52.6 million followers while teammate Neymar has 45.7 million. (IANS)