The Rated People advert displayed on the Tube in London prompted jokes the Duke of Sussex had already found a job after stepping back from royal duties.
But apparent lookalike Simon Pengelly from Brecon, Powys, said he was usually compared to actor Jason Statham.
"That photo was taken back in 2016... I normally have a shaved head," he said.
"Maybe one or two of the boys [have said I look like Prince Harry] because I have a ginger beard but not much really.
"He's not a bad looking chap but I prefer Jason Statham because he's got a bit more of a rep - but any comparisons to anyone is a compliment I suppose."
Responding to an image of the advert, former Conservative MP Mark Prisk tweeted: "Good to see the Duke of Sussex has already found work."
Journalist Emma Lindsay tweeted: "Fair play to Harry, he didn't hang about on his mission for financial independence #Megxit."
Another Twitter user BraillecatRacing tweeted: "Well Harry wanted the common life."
Mr Pengelly, 36, said he had been "inundated" with messages and "banter" from friends - "probably stuff you couldn't say" - since the image was shared on social media.
The self-employed builder and actor, who has made appearances in Being Human and Merlin, said he hoped the attention would provide a boost to his burgeoning acting career.
"At the moment I'm trying to do both the building and the acting, the dream is to step away [from the building]," he said.
As for his thoughts on the Duke and Duchess of Sussex no longer being working members of the royal family, Mr Pengelly said he was "not really bothered".
"I've seen this thing about him going off to Canada but everyone's entitled to their own opinion and to live their own life," he said.
Earlier this month, after the Duke and Duchess said they wanted to "step back" as senior royals and divide their time between the UK and Canada, Buckingham Palace announced they would no longer use their HRH titles, receive public funds for royal duties or formally represent the Queen.
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