The 29-year-old, from Bettystown in Co. Meath, starred in 3 episodes of the hit reality show last month.
The jewellery designer made the move to London during lockdown in November 2020, where he met cast member Paris Smith.
Speaking on RTÉ Radio One, Cillian explained how he got his start in reality TV by challenging 23-year-old Paris to an Irish dance off on a night out.
“I definitely never expected it to happen,” he admitted.
“I met Paris Smith, who’s one of the main characters on the show. I met her the traditional way, face to face. It was in a club in Mayfair and I met her on the dancefloor.
“I approached her on the dancefloor and challenged her to see if she could Irish dance and, to my surprise, she actually could and was much better than me. So, I gave her my number and the rest is history.
“I didn’t recognise her. I’d watched the first few seasons [of the show] but not this one.
“She actually mentioned it to me on the night I met her because I was walking down the road and she sounds quite posh so I was slagging her saying she has one of the most posh accents I’ve ever heard and that she should be on Made in Chelsea.
“And then she replied saying, ‘I actually am on Made in Chelsea.’ I didn’t believe her at all; I just thought she was joking. But then the next morning she followed me on Instagram and I realised she was actually on Made in Chelsea, which was quite funny.”
After the pair had been together for some time, Cillian was invited to appear on the show by producers.
He explained: “After we’d been dating for a while, she wanted me to be on the show and the producers wanted me on so I thought I’d give it a shot. It's a reality TV show, so the producers always want someone as real as possible.
“It was a very new experience for me coming from a finance background. It was pretty cool. You arrive on set, there’s lots going on and you’re the centre of attention, there’s cameras on you.
“I was a bit worried because I can’t act but you’re allowed to talk about anything and there’s no script. It’s organic,” he added.