Joe Biden voted in his hometown of Wilmington, Delaware.
Afterwards, the Democratic presidential candidate took the opportunity to talk about his plans for the US health care system, NPR reports.
He also said he could consider working with Republicans to improve the ACA, the Affordable Care Act, also known as Obamacare.
The reform was launched by then-President Barack Obama in 2010.
- I have a proposal on how we can improve ACA.
Barack and I wanted to add an alternative that allows people to keep their private insurance if they wanted to do so and make it more affordable to choose a better insurance plan.
Trump has promised to tear up Obamacare
In his 2008 election campaign, Obama promised that those who had old health insurance would be allowed to keep them, but many Americans have had their health insurance terminated because their insurance had worse terms than the mandatory "Obamacare" insurance.
They were therefore forced to take out new insurance, with better terms - but more expensive premiums.
On Saturday, President Donald Trump voted in a library in Florida.
Since taking office, he has promised to tear up Obamacare and replace it with a new health insurance system.