And according to palace sources, the dad-of-two marked the milestone privately surrounded by his loved ones.
While his Granny recently had a very public birthday with Trooping the Colour, William decided to stay with his immediate family behind closed doors.
Palace insiders told Hello! that the birthday boy was with his wife Catherine and their two kids, Prince George and Princess Charlotte.
The tight family "tucked into a birthday cake and a meal," the publication report.
It's likely that Catherine whipped up the feast, though she has joked in the past, "William has to put up with my cooking most of the time!"
At the time, Wills was quick to chime in, joking: "It's the reason I'm so skinny!"
That doesn't mean the Duchess doesn't know a thing or two in the kitchen – after all, she famously served up her grandmother's chutney as a Christmas gift to the Queen.
"I can remember being at Sandringham, for the first time, at Christmas," Kate revealed in a documentary released to coincide with the Queen's 90th birthday celebrations.
"And I was worried what to give the Queen as her Christmas present. I was thinking, 'Gosh, what should I give her?' I thought back to what would I give my own grandparents and I thought, 'I'll make her something', which could have gone horribly wrong, but I decided to make my granny’s recipe of chutney."
Admitting she was "slightly worried about it", Kate revealed that the chutney featured in the Christmas meal the following day, noting that it shows the Queen's "thoughtfulness, really, and her care in looking after everybody."
In fact, Kate's prowess in the kitchen shouldn't be that much of a shock, according to former Kensington Palace chef Carolyn Robb she's a pro.
"You have to remember that she’s not royal," the chef told Racked a couple of years back.
"She comes from a normal background and a normal home where she’s always cooked for herself. And what I’ve always heard is that William enjoys spending time with her family because they just eat together at the kitchen table like a normal family. I’m sure that that’s what they still do," she told the site.
And normal family life is just how the Cambridges like to spend their time.
For Princess Charlotte's second birthday in May, the family invited friends and family over for "a little party".
William and Kate have both had busy weeks, from the entire gang including George and Charlotte at the Queen's official birthday at Trooping the Colour, Wills also joined his grandmother to the site of the Grenfell Tower fire in west London, before the majority of the royal family stepping out for Ascot on Tuesday.
We wouldn't be surprised if the pair, who've been married for five years, opted for some takeaway.
While Catherine would always go for curry, it's a tougher a decision for the man of the moment.
"It's a real conundrum when it comes to [takeaway] – pizza, curry or Chinese," William said during a BBC radio chat earlier this year.
"You do struggle for choice,"his wife remarked, with Wills explaining, "I'm not so good with the spicy food!"