The 49-year-old actress sparked dating rumours with the 'Snow Patrol' musician last year, when she attended Jennifer Aniston's Christmas party with him, reported Contactmusic.
"Johnny went home to Ireland over the new year, while Courteney headed to Mexico with Jennifer Aniston. The time apart made her realise how serious she is about him and as soon as he got home she asked him to live with her," a source said.
"This is the happiest Courteney has been in a long time," the source added.