The 31-year-old actress and 46-year-old Tesla co-founder recently broke up after reconciling in December, according to TMZ.
Sources said Heard and Musk split after their renewed relationship "fizzled out." The pair reportedly still care about each other but felt that separating was best.
People confirmed Heard and Musk ended their relationship on good terms.
"Elon decided it was time to end it and Amber agreed," an insider said. "They both still care deeply for each other but the timing wasn't right."
Heard believes she and Musk are better off as friends, according to Us Weekly.
"Amber wants her independence and prefers being friends rather than romantically linked," a source said.
Heard and Musk initially split in August after a year of dating. Musk later said in the Nov. 30 issue of Rolling Stone that his breakup with the actress caused him "severe emotional pain."
"I was really in love, and it hurt bad," he said. "I've been in severe emotional pain for the last few weeks."