The 24-year-old striker, who scored 23 times in Spain’s second division last season, had pulled out of the move earlier on Monday in order to hold talks with Getafe
The 24-year-old striker has committed to a four-year contract with the Scottish champions and is Ronny Deila’s sixth signing this summer following the arrivals of Craig Gordon, Jo Inge Berget, Aleksandar Tonev, Jason Denayer and Mubarak Wakaso.
Scepovic has been capped eight times by Serbia and scored 23 times in Spain’s second division last season.
Scepovic had agreed terms and undergone a medical with Celtic by Sunday evening but pulled out of the move in order to hold talks with Getafe.
"Last night we were told he didn't want to come, he had changed his mind, which was extremely disappointing,” Celtic chief executive Peter Lawwell told Sky Sports earlier on Monday.
"We spent a lot of time on it. We'd agreed with the club and himself. We were just at the point of signing the contract, he'd got his work permit, he'd gone to Paris on Friday to have an appointment with the embassy, which went well. The plan was he was going to go back and pick it up today.
"He passed his medical on Saturday. I spoke to him on his way back from his medical on Saturday afternoon and everything was fine.
"So we were bitterly disappointed and we don't understand it."