Short answer
Call your mobile provider and lock the SIM. The fastest fix is a new SIM with the same number on a new phone: registering WhatsApp there signs the old phone out. Otherwise, email WhatsApp support with “Lost/Stolen: Please deactivate my account” and your number in full international format. Messages to you wait up to 30 days; re-register within that time and you get them and stay in your groups — after 30 days a deactivated account is deleted. Restore chats from your backup, then turn on two-step verification.
Right now: lock the SIM
Call your provider as soon as possible. A locked SIM can’t receive the SMS or call needed to verify WhatsApp again on that phone. But WhatsApp can keep running on Wi-Fi — so also do one of the next two steps.
Fastest: re-register your number
- Get a replacement SIM with the same number.
- Install WhatsApp on the new phone and register the number — this signs out the lost phone.
- Restore from your backup if you have one (made before the phone went missing).
No SIM yet: ask WhatsApp to deactivate
- Email WhatsApp support (the address is on its lost-and-stolen help page) with “Lost/Stolen: Please deactivate my account” in the body.
- Include your phone number in full international format.
- WhatsApp can’t locate the phone, and you can’t deactivate it remotely from another device.
The 30-day window
- Contacts can still message you; messages stay pending for up to 30 days.
- Re-register within 30 days to receive them and stay in your groups.
- After 30 days, a deactivated account is deleted.
Afterwards
- Turn on two-step verification with a PIN and recovery email.
- Watch for scams sent “from you” to your contacts and warn them: “Hi Mum” scam.
- If someone already took over the account, see WhatsApp hacked or our hacked account recovery service.
Frequently asked questions
Does locking my SIM stop WhatsApp on the stolen phone?
Not on its own — WhatsApp can still work on Wi-Fi. Re-register your number on a new phone or ask WhatsApp to deactivate the account.
Will I lose my chats?
You can restore them on a new phone if you have a backup made before the phone went missing.
What happens to messages sent to me meanwhile?
They stay pending for up to 30 days and arrive when you re-register.
Can WhatsApp track my stolen phone?
No. WhatsApp can’t locate devices.
Sources: WhatsApp Help — lost and stolen phones, WhatsApp Help — about account deactivation, WhatsApp Help — back up or restore your chats, WhatsApp Help — account security tips