The rules of etiquette state that women are to cover their shoulders in church and wear a hat to cover their head.
Chloe flashed the flesh in a dusty pink knee-length gown which flaunted her cleavage and pins.
The blonde, who attended the event with her partner James Haskell, wore her plunging dress with a matching fascinator.
However, Chloe’s outfit didn’t go down too well with social media fans.
One user commented: “Chloe Madeley looks SO inappropriate #RoyalWedding.”(sic)
Another penned: “I don’t believe I’ve just seen Chloe Madeley arrive at the church.
“Wearing a sun dress and her shoulders out… *grabbing my pearls and gasping* Judy you should have told her.”(sic)
“Oh no! Chloe Madeley looks lovely but #royalwedding has she left her jacket in the taxi?” a third wrote.
Chloe and James attended the event alongside a host of star-studded guests.
The Royal Wedding guest list included the likes of George and Amal Clooney, Serena Williams and Elton John.
Amal, 40, stood out in an elegant yellow gown with a matching fascinator.
George, 57, colour co-ordinated with his wife by wearing a grey suit and a yellow striped tie.
Another couple who colour co-ordinated are Tom Hardy, 40, and Charlotte Riley, 36, whose appearance whipped fans into a frenzy.
The actor opted for a smart navy suit, while Charlotte stunned in an ankle-length navy adorned in multiple flowers.