WASHINGTON — President Biden made his first late-night show appearance since taking office on Friday, condemning partisanship in Congress and endorsing a song featuring the rapper Megan Thee Stallion to encourage Americans to get the Covid vaccine.

“Not a joke,” he said on “The Tonight Show” with the comedian Jimmy Fallon.

For Mr. Biden, who appeared virtually in the taped interview, his third appearance on the show amounted to a break from criticism over his declining poll numbers and a spike in inflation that last month accelerated at its fastest pace in 40 years. The president used the opportunity to celebrate the passage of his bipartisan infrastructure package, emphasize the importance of voting rights and encourage Americans to get their shots.

“The bottom line is that the way to avoid the virus is to get two shots and then get the booster shot,” Mr. Biden told Mr. Fallon. He added that if more people listened to the song that Mr. Fallon created with the singer Ariana Grande and Megan Thee Stallion, “It was a … Masked Christmas,” it would help combat vaccine hesitancy.

Mr. Biden shared a link to the song on Twitter earlier on Friday with the message, “’Tis the season (to get boosted).”

“It is really important,” Mr. Biden said of the booster shots, noting that teenagers and young people were now eligible to be vaccinated. “We’re moving, we’re moving.”

Mr. Biden also took the opportunity to take a slight shot at the partisan divisions that have become the norm in Congress, after Mr. Fallon said that he saw Democrats and Republicans cordially socializing at the 44th Kennedy Center Honors on Sunday.

“I saw Republicans and Democrats in the crowd — everyone’s laughing at jokes and listening to great music, and everyone seemed cordial and nice and I go, This seems like it should be much easier to get along with everybody,” Mr. Fallon said.

Mr. Biden then noted a reason he was tardy for his taped interview was because he was at the funeral of former Senator Bob Dole, a former Republican presidential nominee who the president eulogized earlier in the day as a blunt leader willing to work across the aisle.

“He asked me on his deathbed whether I would do his eulogy,” Mr. Biden said. “We’re friends. We disagree, but we’re friends. We used to have an awful lot of that relationship and it still exists.”

The president then said the extremist views displayed by some members of the Republican Party had eroded some of that bipartisanship.

Mr. Biden has appeared on Mr. Fallon’s show twice before, both in September 2016, toward the end of his time as vice president and again in 2020, in an interview that took on a much more serious tone during the spread of the coronavirus pandemic. Mr. Biden, who as president will often add emphasis during his speeches or interviews with mentions of “That’s not hyperbole” and “It’s not a joke,” has shown a willingness to joke around a bit on late-night shows.

Mr. Biden told Mr. Fallon how his family was not used to having every meal made for them in the White House and that he reached an agreement with “the guys who run the kitchen” that the first family would make breakfast for themselves.

“You make your own eggs?” Mr. Fallon asked.

“Well, I don’t — Jill does,” Mr. Biden said, referring to the first lady of the United States.

Mr. Biden also foreshadowed some of his forthcoming goals during the appearance on the show. When asked what he hoped he would be talking about this time next year, he said he hoped he would be celebrating his administration getting the pandemic under control, even as the rise of the Delta variant this summer factored into his dwindling approval ratings. He added that he was focused on putting in effect more measures to combat climate change.

And Mr. Biden said that he hoped to pass legislation that would preserve the right to vote, something he acknowledged during a CNN town hall in October that had not received his full attention while he tried to secure enough votes to pass his infrastructure and social spending packages.

Mr. Biden said the Republican attempts to restrict voting rights in more than a dozen states was “literally un-American.”

Mr. Fallon has issued playful jabs at Mr. Biden on his show as recently as last week, when the host played a clip of the president delivering the jobs report through a hoarse voice.

“There he is, President Groot,” Mr. Fallon told his audience, referencing the beloved extraterrestrial tree alien from the “Guardians of the Galaxy” films.