Charlie's tweet comes as Ferne joined the show as a late arrival alongside Vicky Pattison and Spencer Matthews.
Charlie tweeted after Wednesday night's show (18 November): "Good luck @fernemccann" with an emoji face blowing a kiss.
All eyes have been on Ferne and Vicky, as the pair are expected to clash following their past history, but as they entered Snake Rock, the duo were all smiles as they shared several hugs.
Good luck @fernemccann— Charlie Sims (@charlessims_) November 18, 2015
Back in August 2013, Vicky was rumoured to have been spotted on a date with Charlie following his break-up from Ferne, and Ferne later accused Vicky of sleeping with him.
Ferne and Charlie rekindled their romance after that, before splitting for good in March 2015.
Ferne's former TOWIE co-star Gemma Collins has said she thinks Ferne will end up confronting Vicky as they become more settled in camp.
Gemma said: "When Ferne gets a little bit bored she's gonna want to know what happened between her [Vicky] and Charlie. Apparently Vicky and Charlie got it on behind Ferne's back.
"When the cameras are going she'll get going, or she might just say forget it, it's in the past, let's move on."
Before entering the jungle, VIcky said she was keen to avoid confrontation, but called Ferne "quite bitter" before admitting she didn't want the jungle to turn into "some f**king Mean Girls episode".
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I'm A Celeb - full line-up: