“Lady Gaga, oh, I could tell you a few stories about her,” he said, speaking on Monday at a rally in Scranton, Pennsylvania — Mr Biden’s hometown.
“Lady Gaga is not too good.”
The president was equally unimpressed with James — a long-time nemesis, reviled for his friendship with the Obamas and his vocal support for Mr Biden, and for Democrat causes.
Mr Trump said he “felt badly for LeBron” — who won his fourth NBA Championship on 11 October — because Finals ratings were down so much.
He added: “I didn’t watch one shot. I get bored.”
The crowd then erupted into chants of “LeBron James sucks”, to which Mr Trump responded: “What a crowd!”
James has recently said that he had no interest in a social media war with the president.
“I don’t go back and forth with anybody. And I damn sure won’t go back and forth with that guy,” he told the New York Times.
“But we want better, we want change in our community. We always talk about, ‘We want change,’ and now we have the opportunity to do that.”
The president then mocked Jon Bon Jovi, who performed for Mr Biden last week at a rally
“Jon Bon Jovi, every time I see him he kisses my ass,” he said, to whoops from the crowd.
He also ridiculed Beyonce for her backing of the Democrats, mispronouncing her name.
Gaga, who was a strong supporter of Barack Obama and Hillary Clinton, released a clip on Twitter mocking Trump voters as rednecks, dressed in military fatigues and leaning on a huge truck.
“I’m voting for America, which means I’m voting for Joe Biden,” she said in the clip.
In another she dressed up as a Kardashian-style “influencer”, urging young people to be sure to cast their vote.
She posted a photo of her and Mr Biden, who she referred to as “my friend”.
On Monday night Gaga will perform at a drive-in rally in Pittsburgh.
The 34-year-old singer has been getting under Mr Trump’s skin for several days now with her pro-Biden activism, and in particular her membership of Artists Against Fracking, a group founded by Yoko Ono in 2012.
Trump campaign communications director Tim Murtaugh called her an “anti-fracking activist” and said Mr Biden was prioritising “the desires of the liberal Hollywood elite and the radical left.”
She replied: “HEY TIM HEY @realDonaldTrump SO HAPPY IM GLAD TO BE LIVING RENT FREE in your HEAD. #BidenHarris”