Thunberg responded by changing her Twitter profile bio to read: “A teenager working on her anger management problem. Currently chilling and watching a good old fashioned movie with a friend.”
»MORE: Thunberg is Time's 'person of the year'; here are Georgia's young climate activists
In September, Trump was accused of mocking the teen on Twitter after she called out world leaders for not doing enough to tackle the climate crisis.
"She seems like a very happy young girl looking forward to a bright and wonderful future. So nice to see!" Trump posted on Twitter, replying to a video of Thunberg's speech at the United Nations climate action summit earlier in the day.
What you need to know about Greta Thunberg
The next day, Thunberg updated her Twitter bio to read: "A very happy young girl looking forward to a bright and wonderful future."
The Swedish teenager has become a symbol of a growing movement of young climate activists after leading weekly school strikes in her country that inspired similar actions in about 100 cities worldwide.
She has drawn large crowds with her fiery appearances at protests and conferences during the last year and a half.
Trump is the second world leader to take aim at Thunberg this week.
Her recent condemnation of the slayings of indigenous Brazilians in the Amazon drew a harsh rebuke from Brazil's president on Tuesday, when he called Thunberg a "brat" in Portuguese.
»RELATED: Brazil's Bolsonaro calls activist Greta Thunberg a ‘brat’
“Greta said that the Indians died because they were defending the Amazon,” Jair Bolsonaro said. “It’s impressive that the press is giving space to a brat like that,” he added, using the Portuguese word “pirralha.”
Thunberg has since changed her bio on Twitter, where she has more than 3 million followers, to say “Pirralha.”
In 2015, Trump attacked German Chancellor Angela Merkel for “ruining Germany” after she was named Person of the Year, when he was listed as a runner-up.