Amelia was elegant in a black blazer and flowing trousers with a matching waistcoat underneath. Eliza had on a deep raspberry look with black sandals.
The latter sister celebrated the fashion milestone on Instagram with photos from the event. "Our first ever show in Milan @albertaferretti What an incredible experience," Eliza penned.
Amelia also expressed her gratitude on social media, writing, "Thank you for having us @albertaferretti at your beautiful show at Milan Fashion Week."
This was Lady Eliza and Lady Amelia's first fashion show in Milan, but it was not their first time experiencing Fashion Month. The twins already stepped out for this season's events during London Fashion Week with their elder sister, Lady Kitty Spencer.
The sisters stunned at the Perfect Magazine and NoMad London Fashion Week party on Sept. 19 in matching black outfits.
Amelia and Eliza are both represented by Storm Management. The model sisters are the daughters of Princess Diana's brother, Charles Spencer, and former model Victoria Aitken.