Pareto etched her name in the history books in Rio de Janeiro, becoming the first Argentine athlete to win gold in judo after taking out the women's 48-kilogram division.
Her performance in Brazil drew the attention of Argentina's all-time leading goalscorer in football and five-time Ballon d'Or winner Messi.
Enjoying his day off following Barcelona's shock 4-0 pre-season loss to Liverpool on Saturday, Messi took to social media to show his support for Pareto and Argentina.
"Congratulations to La Peque on winning Argentina's first gold in Rio," Messi wrote via Facebook on Sunday.
"All of those years of effort have paid off!
"I hope that this medal is the first of many for our nation at these Olympics!"
Messi's future with Argentina is uncertain after his stunning announcement to retire from international football in June.
The 29-year-old made the surprise revelation after Argentina suffered a heartbreaking penalty shoot-out loss to Chile in the Copa America Centenario final last month - his fourth defeat in major finals in nine years.
New Argentina head coach Edgardo Bauza is now planning to speak with Messi to see whether 113-cap veteran will return to the international fold.