How to Activate an AT&T SIM Card

What you need to do to activate an AT&T SIM card

To activate an AT&T SIM card, you'll need your SIM card, a phone that works with AT&T's network, and either a phone number you're bringing from another carrier or a new number AT&T will assign you. You can activate through AT&T's website, the AT&T mobile app, by calling 611 from an AT&T phone, or by visiting an AT&T store in person. The process takes about 15 minutes if you do it online or through the app, and a few minutes longer if you call or visit a store.

The main thing to know upfront: activation connects your SIM card to AT&T's network and links it to a phone number and billing account. Until you complete this step, the SIM card won't work, and you won't be able to make calls, send texts, or use data.

Key Takeaways

• You can activate an AT&T SIM card online at att.com, through the AT&T mobile app, by calling 611, or at an AT&T store location.
• Online and app activation usually takes about 15 minutes and is the fastest option if you have your account information ready.
• If you're moving your phone number from another carrier, you'll need your account number and PIN from that carrier to complete the transfer during activation.
• Once activation is complete, your SIM card will connect to AT&T's network within a few minutes, though it can take up to 24 hours in rare cases.

Activating through AT&T's website or mobile app

The online method is usually the fastest. Go to att.com/activate or open the AT&T mobile app and select "Activate a device." You'll be asked whether you're a new customer or an existing AT&T customer. If you're new, you'll create an account and choose a phone number or transfer one from another carrier. If you're existing, you'll sign in with your current AT&T username and password.

Have your SIM card number ready — it's printed on the card itself and also on the packaging it came in. You'll also need to know your phone's IMEI number, which you can find by dialing *#06# on the phone or looking in the phone's settings under "About Phone." The website or app will walk you through entering this information and confirming your billing address.

Once you submit, AT&T will send you a confirmation email. Insert the SIM card into your phone, restart it, and your phone should connect to AT&T's network within a few minutes. You can check your signal bars to confirm the connection is active.

Activating by phone or in an AT&T store

If you prefer to talk to someone, call 611 from any AT&T phone or call 1-800-331-0500 from any other phone. An AT&T representative will walk you through the same information you'd enter online — your SIM card number, phone IMEI, and whether you want a new number or to transfer an existing one. This method takes about 10 to 15 minutes depending on how busy the line is.

You can also walk into any AT&T store with your SIM card and phone. A store employee will activate it for you on the spot, usually in under 10 minutes. This is the best option if you're not comfortable doing it yourself online or if you run into any problems during the process.

Transferring your phone number from another carrier

If you're keeping your current phone number and moving it to AT&T, you'll need information from your current carrier. Before you start activation, contact your old carrier and ask for your account number and account PIN. Some carriers call this the "transfer PIN" or "port PIN." You'll enter this information during the activation process so AT&T can request your number from the other carrier.

The transfer itself usually takes 24 hours, though it can happen faster. During this time, your old phone may stop working, or both phones might work briefly. Once the transfer is complete, your number will ring on your AT&T phone, and your old carrier will send you a final bill for any remaining balance.

What to do if activation doesn't work

If you've completed activation but your phone still shows no signal, restart your phone first — this solves the problem about half the time. If that doesn't work, check that you've inserted the SIM card all the way into the slot. Some phones have a small tray you pull out; others have a slot you insert the card into directly. Your phone's manual will show which type yours is.

If you still have no signal after 30 minutes, call 611 from another phone or visit an AT&T store. Activation can occasionally fail if there's a mismatch between your SIM card number and phone IMEI in AT&T's system, and a representative can fix this by re-running the activation or issuing you a new SIM card.

How long activation takes

Online or app activation is instant — you'll get a confirmation email within minutes. However, your phone may take a few minutes to a few hours to connect to AT&T's network after you insert the SIM card and restart. In rare cases, it can take up to 24 hours. If you're transferring a phone number from another carrier, that transfer takes up to 24 hours separately from the SIM card activation.

If you're activating in a store or by phone, the representative will complete the activation while you're there or on the call, and your phone should connect to the network within a few minutes afterward.

Frequently Asked Questions

Do I need an AT&T account before I activate my SIM card?

No. If you're a new customer, you can create an account during the activation process itself. If you're already an AT&T customer adding a new line or device, you'll sign into your existing account. Either way, activation and account setup happen together.

What if I don't know my phone's IMEI number?

Dial *#06# on the phone and the IMEI will appear on your screen. If that doesn't work, go to Settings, then About Phone, and look for IMEI or Serial Number. You can also find it printed on the phone's original box or on the back of the phone itself on some models.

Can I activate a SIM card that came with a phone I bought somewhere other than AT&T?

Yes, as long as the phone is unlocked and compatible with AT&T's network. Most modern phones work with AT&T. If you're unsure, you can check AT&T's website by entering your phone's model, or ask an AT&T store representative before you buy the SIM card.

What happens to my old phone number if I don't transfer it during activation?

If you don't transfer it, you'll get a new AT&T phone number. You can transfer your old number later by contacting AT&T, but the sooner you do it during activation, the simpler the process is.

Will my SIM card work immediately after activation, or do I need to wait?

Your SIM card should work within a few minutes of activation, though it can take up to 24 hours in rare cases. Restart your phone after inserting the SIM card to speed up the connection. If you don't see signal bars within an hour, contact AT&T to troubleshoot.