Schumer made the endorsement Saturday night in front of 750 people at Hy-Vee Hall in Des Moines, The Des Moines Register reported.
"I have found my 2016 candidate," Schumer said. "She's a virtual guarantee to deliver victory for our party in 2016."
Before speaking at the event, Schumer tweeted his support for Clinton, who represented New York in the Senate with Schumer before joining President Barack Obama's cabinet in 2009, The New York Times reported.
"Run, Hillary, run," Schumer tweeted. "If you run, you'll win and we'll all win. With a strong platform and with Hillary leading the charge, we will vanquish the Ted Cruz Tea Party Republicans in 2016."
Clinton has not said whether she plans to run for president in 2016.