Both royals were without their spouses for the occasion. Prince William is currently in New Zealand to pay tribute to those affected by the Christchurch mosques terrorist attack, while Meghan Markle is due to give birth to her and Harry's first child any day now.
The royal duo seemed perfectly relaxed without their significant others as they entered Westminster Abbey.
Harry looked dapper in a deep blue suit, a look that has become his signature in recent years.
The Duchess of Cambridge stood out in a teal custom coat dress, which featured an elegant pleated skirt by Catherine Walker. The silhouette has become a favourite of Kate's for official engagements.
The mother-of-three accessorised with a matching feather fascinator, and contrasting bottle green court heels and clutch bag, both by London-based brand Emmy London. The suede bag retails for £350 and £425 shoes. Shop it here.
The ensemble was also paired with dazzling topaz and diamond jewellery. The duchess wore a 18ct white gold flower necklace (£1,500) and matching drop earrings (£3,500) both by British designer Kiki McDonough.