Their relationship was said to be fractured after Cole was axed from Cowell's X Factor USA last autumn.
When asked whether the pair's friendship is back on track, the Syco boss told Live magazine: "I think it is, yeah - we text occasionally.
"I mean she's not on the phone every night anymore, but she broke the ice when she sent me that funny birthday message. I thought it was hilarious. I loved her for it."
In October, Cole sent an aeroplane over his house trailing a banner that read, 'Simon Cowell is 52 today. Ha ha ha. Love Cheryl'.
However, referring to her X Factor dismissal by US network Fox, Cowell added: "I know when I've crossed the line a little bit.
"I thought there was going to be a big reaction. I wasn't prepared for what was coming next. I had to apologise for the way it was handled."
Despite persistent rumors suggesting the contrary, the 'Promise This' singer has insisted that she will not return to the UK version of The X Factor, having quit the ITV talent show last year.
> Simon Cowell still wants Cheryl Cole on The X Factor