How to train a puppy to be alone in another room?

A closed door removes every sense the puppy relies on to feel safe, which is a big jump from constant togetherness. A baby gate lets the puppy see and hear you moving around the house while still learning that physical closeness is not required every second, which is an easier first step.

Give the puppy a stuffed chew, step behind the gate, stay within sight for 30 seconds, then return calmly before returning to your normal activity. Repeat several times a day, gradually moving further out of sight and staying away longer as the puppy settles quickly each time.

Go back before whining turns into sustained barking or scratching at the gate, since returning at the peak of distress can accidentally reward the escalation. A puppy that is quiet, even briefly, right before you return learns much faster that calm behavior is what brings you back.

Once a puppy is reliably calm with a gate separating one room, the same sequence works for extending to a second room, a closed door instead of a gate, or eventually a genuine departure from the house, always by reducing one variable, such as sight or sound, at a time rather than changing several things at once. This steady, one step approach tends to produce a puppy that generalizes well to new alone time situations later, rather than one that only copes in the exact setup it was first trained in.