The event unveiled 11 US Postal Service stamps to commemorate de la Renta, who died in October 2014, at the end of a New York fashion week striking for its virulent opposition to President Donald Trump.
De la Renta moved to New York in the 1960s, his elegant and glamorous clothes coming to define American fashion for five decades, dressing generations of first ladies and creating a multi-million-dollar fashion house.
"Oscar de la Renta was an immigrant," said Clinton, the former Democratic presidential nominee in a rare speech since her loss to Trump last November.
The former secretary of state and first lady, who won the popular vote but lost the electoral college to Trump, could not resist a veiled dig at her former opponent who clashed with the judiciary over his attempt to temporarily suspend immigration from seven Muslim-majority countries.
"What a fitting person to be chosen by our postal service, mentioned by the way in the constitution -- something we should all read and re-read in today's times," she said to more cheers.
Vogue editor-in-chief Anna Wintour, herself British-born, struggled to fend off tears as she paid moving tribute to her late friend.
Wintour and much of the New York fashion industry supported Clinton's quest to become the first woman commander-in-chief.
"To Oscar and to all of us, Mrs Clinton was someone who lived in the public eye with dignity and grace," said Wintour.
"I know Hillary misses him as much as I do.
Disclaimer: No Business Standard Journalist was involved in creation of this content
