Jana Burceska, who revealed she was pregnant in the live TV interview during voting, then introduced the father of her child, Alexander.
Taking the microphone, he dropped to one knee, saying: "I was waiting for the right moment. I love you very much. Would you marry me?"
A surprised Jana squeaked: "Yes!"
The audience erupted into huge cheers as the couple embraced and Alexander presented Jana with a ring.
As she took the ring out of the box, Eurovision host Timor Miroshnychenko said: "I don't know even what to say. It's our first Eurovision proposal."
The moment was missed on the BBC Four's coverage as the camera had cut away to presenters Mel Giedroyc and Scott Mills.
The BBC explained why this happened, saying it could not have "foreseen this" as "the proposal was obviously a surprise".
"The marriage proposal took place in an advert break - as the BBC does not show adverts, it prepares extra content to run in its place," it said.
"We have made the proposal available on the BBC Eurovision website for fans to enjoy. Congratulations to the happy couple!"
Unfortunately for Macedonia, which is also referred to as FYR Macedonia, Jana was voted out of Saturday's final - along with Ireland for the fourth year running. The final will be screened on BBC One at 20:00 BST.
But with a baby and now a wedding to plan for, she is likely to be extremely busy, regardless of her singing schedule.
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Macedonia's Eurovision entrant squealed with delight as her fiance proposed to her in front of an audience of millions during the second semi-final in Kiev.