Their Bloom-ing bromance ended in heartbreak.

Eric Adams privately felt betrayed when Michael Bloomberg endorsed Andrew Cuomo over him for mayor earlier this year, according to a new tell-all book by his ex-girlfriend and sports czar Jasmine Ray.

“Eric brushed it off publicly, but privately, I could hear the crack in his voice,” Ray wrote in her memoir, obtained by The Post.

“He admitted that people he admired had broken his heart. Bloomberg was one of them.”

The glimpse into Adams’ sorrow is one of many shocking intimate moments revealed in Ray’s upcoming self-published book “Political Humanity,” set to come out Sunday.

Adams had basked in his victory in 2021’s mayoral election, not least because Bloomberg took him under his wing, Ray wrote.

He took Ray — with whom he had an intimate relationship years earlier — to Staten Island’s boardwalk and gushed to her about the former three-term mayor’s mentorship, she wrote.

Bloomberg was putting him through “mayor school,” Adams said, according to the book.

“His gratitude in that moment was undeniable; you could hear the respect in his voice and see it in the way he recounted their conversations. But even admiration has its shadows,” the book reads.

As scandals rocked Adams’ first term, Bloomberg jumped ship.

He endorsed Cuomo in June for both the Democratic primary and the general election — and threw millions towards a pro-Cuomo Super PAC.

Bloomberg’s reps declined to comment.

— Additional reporting by Carl Campanile