The 57-year-old "The X Factor" creator has revealed that he was not happy when Horan, 23, chose to sign a solo deal with Capitol Records US rather than his Syco label, reported Femalefirst.
"He probably would have had a number one single if he'd stayed with me. But you know who does have a number one this week? James Arthur. Very pleased he's back with us with a fantastic record. Hashtag loyalty," he said.
Horan recently signed his huge record deal with Capitol US just weeks after Cowell predicted that the star singer would join his label as a solo singer.