Do You Need to Leave the DS On for Nintendogs Breeding?

No. Breeding progresses via the internal real-time clock, not active playtime.

Breeding Process

1. Have compatible male + female dog (same breed group, good friendship).
2. Go on walks together multiple times → "Meet" events.
3. Heart icons appear → "Try for Puppies" option unlocks.
4. Select it → Save the game.
5. Turn off DS. Gestation takes ~2–3 real days (varies by breed).
6. Power on later → puppies born.

Critical: Save Before Powering Off

If the battery dies or you reset without saving, the breeding event is lost. The clock keeps running, but the "pregnant" flag isn't written.

Note: Time-traveling (changing system clock) can confuse the game—avoid it.