Mr Obama passed the Affordable Care Act (ACA) in 2010, and sign-ups under the law have increased under Mr Biden’s tenure, and more generous taxpayer subsidies have cut costs for enrollees, albeit temporarily.
“It’s good to be back in the White House. It’s been a while,”Mr Obama said after he was introduced by Vice President Kamala Harris. He opened by jokingly referring to Mr Biden as “vice president”.
Mr Obama said he and Mr Biden accomplished “a lot” in their eight years as stewards of the country, but “nothing made me prouder than providing better health care and more protections to millions of people across this country".
“The ACA was an example of why you run for office in the first place,” Mr Obama said, calling it the “high point of my time here".
Mr Obama remains a popular figure within the Democratic party, while a recent Gallup poll showed Mr Biden's approval rating sits at just 42 per cent amid rising inflation, Russia's invasion in Ukraine and the ongoing coronavirus pandemic.
His low approval means Democrats are likely to lose one or both chambers of Congress in the midterms, delivering a devastating blow to Mr Biden's agenda.
In addition to delivering remarks, the two were expected to have lunch together, White House Press Secretary Jen Psaki said.
"They are real friends, not just Washington friends," Ms Psaki said.
The Biden administration unveiled a measure on Tuesday to fix an element of the ACA, or "Obamacare", known as the "family glitch" that left family members of those with access to affordable employer-provided health plans ineligible for certain subsidies.
People tripped up by the family glitch are dependents of workers who have an offer of employer coverage that the government interprets as being affordable. As a rule, people with affordable employer coverage are not eligible for taxpayer-subsidised ACA plans.
"It's a common issue. 85 million Americans who can't get financial help to get coverage under the Affordable Care Act," Mr Biden said. "We're going to change that."
The White House estimates 200,000 uninsured people will be able to receive coverage and cut costs for 1 million more.
Obamacare was the former president's signature piece of legislation, and Republicans for years have tried to repeal it. The law has been upheld by three Supreme Court decisions.
"Over 31 million people now health insurance through the Affordable Care Act. Four out of five Americans can find quality coverage. For under $10 a month," Mr Biden said. "The bottom line is this the Affordable Care Act is stronger now than has ever been today."
There are more fundamental issues for the two presidents to consider as well, both policy-wise and politically.
Unless Democrats in Congress finally coalesce around a version of Biden’s social legislation, his enhanced financial assistance for millions purchasing ACA plans will expire at the end of this year.
A return to higher premiums would likely trigger an increase in the number of uninsured people, a political embarrassment for Democrats committed to expanding coverage.
The Biden legislation, which passed the House but sputtered in the Senate, also includes a mechanism for providing coverage to as many as 4 million uninsured low-income adults in states that have refused the health law’s Medicaid expansion. It would deliver on Mr Biden’s campaign promise to build on existing government programs to move the US closer to coverage for all.
Agencies contributed to this report