James had endorsed Clinton as the candidate best able to continue the legacy of Barack Obama.
James, who led the Cleveland Cavaliers to last season's NBA title, had endorsed Clinton as the candidate best able to continue the legacy of Barack Obama, America's first black president.
He and the Cavs' J.R. Smith appeared on stage with her at a rally on Sunday, hoping to boost her in the key state of Ohio, which eventually went to Trump.
James was clearly troubled by the outcome of a campaign during which Trump pledged to deport illegal immigrants, ban Muslims from the country and was heard on a video bragging that he groped women without their consent.
"Parents and leaders of our children please let them know they can still change the world for the better!" James said.
"Don't lose a bit of faith! They're our future and we must remain stronger than ever!! ... Minorities and Women in all please know that this isn't the end, it's just a very challenging obstacle that we will overcome!!"
Smith posted a picture on Instagram of his daughter in front of the White House, asking how he should explain the election result to her.
"You can be an educated women in your field and not get the job because your a women or cause your black? How do you say 'go try your best' even though it won't be good enough," he wrote.
The reigning NBA champion Cavaliers are due to visit Obama at the White House on Thursday, the visit to celebrate their title arranged to coincide with their trip to Washington to play the Wizards on Wednesday night.
On Wednesday, Obama announced that he has also invited Trump to the White House on Thursday so that the president-elect can begin the transition to power.