The actress’ co-stars were quick to send their well wishes in the comments.
“Happy birthday Hennie. What a beautiful big boy you are,” wrote Lynne McGranger, while Sam Frost added, “Aww Happy birthday Henry!”
Emily and her ex partner Paul Jackson welcomed Henry into the world on 3 August 2015 after the actress underwent IVF. The couple separated a year later.
In December, Emily spoke candidly to TV WEEK about her fears as a mother.
"Every day is a reminder of how you have to stay alive as long as possible," she told the publication.
"Because I had him so late in life, I'm very aware of the fact that my mother died very young, so I don't want that to happen to me. So I'm really conscious of eating properly, exercising and looking after myself, to give myself the best possible chance of being there for his 40th birthday."
Emily's beloved mother Glenn was there for her 40th birthday, but only just. She lost her battle with cancer in May 2010.
The actress had returned to Australia from the UK the previous year to look after her. It was then that Home And Away asked her to return as Marilyn, a role she'd first played in 1989.
Emily also revealed that Henry has visited the famous Home and Away set but is too young to understand what her job is.
"He thinks it's normal that there's a picture of Mummy in the magazine,” she said.
“He's too young to watch Home And Away. I tell him that I work in television, but I don't think he really understands what that means.”