Napoleon cake can usually be kept in the fridge for 2 to 3 days if it’s stored covered and kept at a refrigerator-safe temperature of 0–4°C (32–40°F).

Best practice

Keep it in an airtight container or wrap it well so the pastry does not absorb fridge odors and the layers don’t dry out.

Quick note

Because Napoleon cake has custard or cream filling, it’s best eaten sooner rather than later for the best texture and safety.

TL;DR: 2–3 days in the fridge.