"There are folks that are trying to completely purchase our political system, running as Republicans and now tossing in their hats as Democrats in the field as well," she said.
"But what we're here to say is that in a democracy, it shouldn't matter how much money you have. What should matter is whether you vote, whether you caucus, whether you turn out. It's the numbers. It's the people. it's the movement."
Her comments came one day after Bloomberg filed to run in Alabama's Democratic presidential primary. Although he hasn't formally launched his campaign, Bloomberg's wealth would appear to make him a prime target for more progressive politicians like Ocasio-Cortez.
Bloomberg, a perceived moderate, won two New York City mayoral elections as a Republican before winning a third term as an independent. In 2018, he switched his party affiliation to Democrat, saying he was "far away" from the Republican Party and wanted Democrats to provide the "checks and balances our nation needs so badly."
The 77-year-old Bloomberg has previously panned Ocasio-Cortez's signature legislation -- the "Green New Deal" -- arguing that it stood "no chance" of passing the Republican-controlled U.S. Senate. Instead, he pledged to spend $500 million on closing every coal-fired power plant in America by directing money towards lobbying efforts and electing local politicians.
Also Saturday, Ocasio-Cortez addressed skepticism of her plan -- specifically attacking wealthy opponents as "elitist."
"Almost right after I got sworn in, there was a Republican member that told me that caring about the climate was elitist ... as though billionaires aren't buying up their enclaves, thinking they can protect themselves from this. What's elitist is thinking this isn't a problem," she said.
"What is elitist is thinking that you can buy yourself immunity from the floods and the wildfires and the droughts. That is what is elitist. What's elitist is thinking that you can sit on a pile of money and you will be okay while your neighbors aren't. That is elitist," she added, prompting applause.
Fox News' Andrew Craft contributed to this report.