The attacker for Paris Saint-Germain scored twice in a thrilling six-goal thriller, with Lionel Scaloni's team winning on penalties.
Argentina had twice lost at the World Cup's last hurdle in 1990 and 2014, the latter of which had Messi on the losing side. This victory completed a 36-year drought for World Cup gold.
Messi ultimately won the biggest trophy after scoring seven goals and winning the Golden Ball as the tournament's top player. He then turned to social media to express his feelings.
"I dreamt about it so many times; I wanted it so much that I still can't believe it," he posted on Instagram.
"Thank you so much to my family, all who support me, and all who believe in us. We prove once again that Argentinians when we fight together and are united, we can achieve what we aim for.
"The merit of this group, which is above individuals, is the strength of all fighting for the same dream that was also one of all Argentinians... We did it!!!"
Awarded player of the match in the final, Messi was expected to feature in a post-game press conference but skipped attendance as celebrations continued with the squad.
However, he spoke on the field following Argentina's triumph and clarified his desire to continue representing his nation.
"I enjoy being in the national team, the group, I want to continue living a few more games being world champion," he told TyC Sports.