The Oscar winner and environmentalist told the Scottish Business Awards in Edinburgh last night that campaigners could face “a lot of work to do” after Mr Trump takes office in January.
In the run-up to his victory earlier this month, the Republican candidate described climate change as a Chinese hoax designed to put the US economy at a disadvantage.
He has promised to “scrap” much existing environmental regulation and revive the country’s ailing coal industry.
The tycoon has also threatened to withdraw the US from the Paris Agreement, which came into forces earlier this month, committed to limiting global warming to no more than 2C above pre-industrial levels.
At the Edinburgh International Conference Centre last night, DJ Chris Evans drew applause from the audience when he told the star of films including The Revenant, Titanic and The Wolf Of Wall Street that he “guessed” he had not voted for Mr Trump.
DiCaprio replied: “It has been a very interesting election in our country.”
He added: “If this current administration follows through with a lot of things that they have promised on the campaign trail then we have a lot of work to do.
“There’s been mentions of dismantling the Paris agreement, taking away funding from the UN, drilling again, and, you know, unfortunately there’s a lot to talk about over the next four years.
“But I think that the environmental movement has already spoken out loudly that we’re not going to allow these things to happen, and if I think if they want to follow through on these promises there will be an uprising and a strong backlash.”
Earlier, DiCaprio was mobbed by fans as he visited an Edinburgh restaurant that helps the homeless. He was invited to the latest Social Bite venture by co-founder Josh Littlejohn, following in the footsteps of fellow actor George Clooney.
Hundreds of fans braved typically cold and wet weather to greet DiCaprio when he stopped for lunch at the Home restaurant in Queensferry Street in the city’s west end.
Dressed in a dark blue suit, the Oscar winner posed for selfies and signed autographs before joining guests, including Evans and comedian Rob Brydon for lunch.
Elise Lovell, 45, who won the chance to have lunch with the star, was also present, and sat across from the actor.
For Biffy McKay, who was homeless for five years before joining Social Bite, the day was particularly special.
The trainee chef, who helped prepare lunch for the star, said: “I steamed his couscous. He’s having lamb tagine.
“I told him I’ve loved him since I was nine and that I did a project about him at school. He said, ‘That’s so cool’.”
She said meeting DiCaprio had boosted her self-belief.
“When you are homeless people don’t look at you, they look through you,” she said. “I didn’t feel like person back then, I felt invisible. Now I have totally turned my life around. It has given me such a big confidence boost to cook lunch for Leo DiCaprio. I have loved him since I was little girl – it’s a dream come true.”