His body was found near Minyon Falls, a waterfall situated in a national park close to Australia’s Gold Coast.
Police say the death is not being treated as suspicious.
Unwin joined the long-running soap as the rebellious McGregor for a four-year stint between 1996 and 2000, and reprised the role in 2002 for another three years.
His co-stars in the much-loved series paid tribute to the actor upon hearing the news.
Kimberley Cooper, who played Gypsy Nash between 1998 and 2002, posted a picture to Instagram of the pair printed on a magazine cover.
In the caption, she wrote: “My first TV week cover was with you.
“We had years of laughter, be it giggles on set trying to get through scenes as lovers or doubled over belly laughs at the pubs after work.
“I will be sad for now, but I promise to tell stories of great joy about our times together.
“You forever hold a special place in my heart. Love you Onion.”
Dan Bennett, a former script producer on the show, said he was “devastated” by the news.
“Ben was an utterly lovely guy,” he added.
Speaking to Yahoo Lifestyle, Ada Nicodemou, who played McGregor’s former girlfriend Leah Patterson-Baker, said: “I just woke up to the tragic news of Ben’s passing, my heart goes out to his family.”
A spokeswoman for Lynne McGranger, who plays long-running character Irene Roberts, told Australian media that she was “deeply saddened”.
Unwin was nominated for several awards during his Home and Away tenure, including a Logie Award for Most Popular New Talent and a British National Television Award.
He later graduated with a degree in law, and worked as a solicitor in Sydney after leaving the soap.