Goals from the Barcelona icon's forward partners Lautaro Martinez and Sergio Aguero were enough to propel Argentina from bottom of Group B to second and into a quarter-final meeting with Venezuela on Friday at Rio's Maracana stadium.
"The important thing was to win to keep going in the Copa, to get through the group stage," said Messi, who will turn 32 on Monday.
"This will be an important boost for what's to come ... another Copa begins now".