The Whole Cake Island arc in the One Piece anime ends with episode 877 , titled “The Parting Time – Pudding’s Last Wish.”

This is the episode where:

  • The Straw Hats and their allies finally and fully escape Totto Land and Big Mom’s territory.
  • Sanji learns about Pedro’s death and remembers their time together, while Carrot breaks down and he comforts her.
  • Cotton candy-like snow falls as the crew realizes they’re truly leaving Big Mom’s seas behind.
  • Pudding’s feelings are highlighted through a flashback to her kiss with Sanji and her erasing his memory of it.
  • Big Mom’s forces, Jinbe, the Sun Pirates, Germa 66, and Katakuri’s situation are briefly followed to close out the arc.

So if you’re watching and want to finish the Whole Cake Island arc before moving on (into Reverie/Wano), you should watch through episode 877.

In most community and guide discussions, when people ask “what episode does the Whole Cake Island arc end,” the accepted answer is episode 877, because that’s when the Straw Hats’ escape and Pudding’s farewell are wrapped up.

TL;DR:
Whole Cake Island ends at episode 877 – “The Parting Time – Pudding’s Last Wish.”

Information gathered from public forums or data available on the internet and portrayed here.