How to Activate AT&T Sim Card: A Step-By-Step Guide

Whether you're the proud owner of a new phone from AT&T—or bringing your own unlocked device to the network—you'll need to activate your AT&T SIM card to connect to the AT&T network. This is a crucial step because your SIM card tells cell towers who you are and enables you to make calls, send texts, and access the Internet from your cell phone using mobile data.

The good news is that activating an AT&T SIM card is pretty easy, especially with this step-by-step guide. 

If you’re still in research mode, our free, unbiased Plan Finder can help you compare the best phone plans at AT&T and other top carriers. Likewise, our Phone Deal Finder below can help you zero in on the best phone deals available now.  

Step-by-Step AT&T SIM Card Activation Guide

Activating your AT&T SIM might seem confusing at first, but it’s not a complicated process. The steps are slightly different depending on whether you’re activating a phone from AT&T or bringing your own device to an AT&T plan, and there are also different instructions for physical and embedded SIM cards (aka eSIM). Before we dive in, here’s a quick overview of the difference between a physical SIM card and an eSIM and how to tell which type of SIM you have.

A physical SIM card is a small, removable plastic card that contains a microchip with subscriber data and carrier information. An eSIM serves the same purpose, but it is embedded within your device and cannot be removed.

While eSIMs are becoming more common,  physical, removable SIM cards are still very much a thing. Some phones also come with a removable SIM card and eSIM capability. The exception is newer Apple iPhone models, specifically the iPhone 14 and 15 series — these newer iPhones are eSIM-only and do not have a physical SIM card. At the end of this section, we’ll go through how to activate an AT&T eSIM.

As of the writing of this article, unless you are activating an iPhone 14 or 15, you can count on your cell phone having a physical SIM card in a removable tray located on the side or bottom of the phone. If you bring your own device (BYOD) to AT&T, your existing SIM card might work on AT&T’s network, or you may need a new AT&T SIM card — more on that later.

But first, let’s walk through how to activate a brand new AT&T phone plan and device for physical SIM cards.

AT&T SIM Card Activation Steps: Physical SIM Card on a New Phone From AT&T

If you purchase a device at a brick-and-mortar AT&T store, an AT&T representative may guide you through the activation process or do it for you. However, if you purchase a phone online and have it shipped directly to you, you’ll have to activate it on your own. The good news is that activating your AT&T SIM card on your own is simple:

1. Go to the activation page on the AT&T website and scroll down to “Choose your service.” Note that you can complete this process using a desktop or tablet browser or your phone.
2. Select the type of plan you want to activate: AT&T Wireless or AT&T Prepaid. Wireless plans typically involve a contract and monthly payments, and prepaid plans operate on a pay-as-you-go basis.
3. Follow the instructions on the AT&T activation portal to activate the device. You might need to enter either the ICCID/SIM number on your SIM card or the last four digits of the EID number printed on your device packaging.
4. When prompted to enter your IMEI number, check your device packaging and your device settings. On an Android phone, it will be under Settings > About Phone > Status. On an iPhone, check Settings > General > About.
5. Complete the activation process by following any additional prompts.

AT&T SIM Card Activation Steps: Bring Your Own Device with a Physical SIM Card

If you choose to bring your own device (BYOD) to AT&T instead of buying a phone from AT&T, the SIM card activation process is a bit different. With BYOD, since the device isn’t from AT&T, it won’t have an AT&T SIM card pre-installed, and you may need to either physically swap out your previous SIM card or do it digitally with an eSIM. 

Follow these steps if you’re activating an AT&T plan on a device you didn’t purchase from AT&T: 

1. If you previously used your BYOD phone with another carrier, you should start by contacting your current carrier to confirm their transfer requirements.
2. Next, visit AT&T’s BYOD portal and follow the prompts. 
3. The portal will confirm that your device is unlocked and compatible with AT&T’s network. It will also let you know whether you can use your existing SIM card with AT&T. If not, you can purchase a new SIM card kit from AT&T during the compatibility check.
4. Once you check transfer requirements and confirm device compatibility, the BYOD portal will also guide you through the activation process.

AT&T SIM Card Activation Steps: eSIM on a New Phone or BYOD

Although removable SIMs are still the industry standard, many devices now support dual SIM functionality and multiple embedded SIMs (eSIMs). If your phone has both a removable SIM card and an eSIM, follow the instructions above and use the physical SIM card for your primary phone plan. If your phone is eSIM-only (for now, that’s only Apple iPhone 14 and 15 users), you’ll activate your primary plan on an eSIM.

Whether you buy a new phone from AT&T or BYOD, you may choose to activate a secondary line for convenient international travel or work purposes. This is where eSIM capabilities really come in handy for many users.

Activating an eSIM from AT&T is so straightforward it’s almost automatic. Follow these steps:

1. First, make sure your phone is connected to a WiFi network or cellular service.
2. Open Settings.
3. Select “AT&T plan ready to be installed” and Continue.
4. Your eSIM will download and install.

Next Steps: Setting Up Your Device

If you’re simply bringing your old phone to a new carrier, your phone is likely already set up just the way you like it, but if you’re getting started with a brand-new phone, you’ll need to finish setting up your device. If it’s a new Android or Apple phone, the device should automatically provide setup instructions when you turn it on. During the initial setup, you’ll select your language, region, and other device preferences. You’ll also set up device security.

Most devices will guide you through options for transferring data from your old device or cloud storage systems like iCloud or Google Drive. You’ll also want to install your favorite apps and get logged in to your accounts, including email and social media profiles.

Device manufacturers and carriers alike try to make switching to a new phone as seamless as possible. Remember, you can always call a customer support number or visit an AT&T store for extra help. 

Troubleshooting AT&T SIM Card Activation Process: All Phones and SIM Types

In a perfect world, the SIM Card activation process will go smoothly, and you’ll be connected to “America’s favorite network” in no time. But just in case, here are some troubleshooting tips to try if you run into any issues while activating your AT&T SIM card or eSIM. 

Check SIM Card

First, if your phone has a physical, removable SIM card, make sure it’s inserted correctly and check it for damage. The AT&T logo should face up, and the metal contacts should face down. If your phone has two physical SIM card slots, make sure your SIM is inserted into slot 1. If your SIM card is visibly cracked, chipped, or bent, or if the metal contacts look scuffed or corroded, you may need to request a new one from AT&T.

Refresh Settings

Next, try the classic tech troubleshooting tip — turning your device off and back on. Then, try turning airplane mode on and off. If that doesn’t work, try resetting your network settings. To do this on an iPhone, go to Settings > General > Transfer or Reset iPhone > Reset > Reset Network Settings. On an Android phone, go to Settings > System > Advanced > Reset options > Reset network settings.

Sometimes, SIM activation and connecting to the network just takes a few minutes, so be patient after trying each of these steps.

Check Network Connection

SIM activation may fail if you don’t have a strong enough signal. Make sure you’re in an area with adequate network coverage while activating your AT&T SIM card. If necessary, move to a location with better reception and try again. 

Verify Account Information

Double-check your account information and settings, and make sure you’ve typed everything correctly on the AT&T activation website. It’s all too easy to misread or mistype a long IMEI or SIM number. 

Contact Carrier

If the above troubleshooting tips don’t work, it’s time to contact AT&T for assistance. Call AT&T support or visit a store to speak with a knowledgeable representative. 

The Bottom Line

Activating your AT&T SIM card should be a smooth, straightforward process, and hopefully, this AT&T SIM card activation guide is all you need to get up and running. 

In the meantime, if you’re in the market for a new phone, our Phone Deal Finder can help you find the best phone offers from AT&T and other top wireless carriers in a matter of seconds. We also keep up-to-date lists of the latest phone deals at AT&T, T-Mobile, Verizon, UScellular, Spectrum Mobile, Xfinity Mobile, Cox Mobile, and Optimum Mobile. 

Frequently Asked Questions

What do I do if my SIM card won't activate?

If your SIM card isn't activating, there are a few quick fixes to try. Start by switching your phone to airplane mode and back again, or simply reboot the device. You can also pop out the SIM card, give it a gentle wipe, and make sure it’s properly seated when you reinstall it. If the issue persists, test the SIM in another phone to rule out hardware problems. 

Why is my SIM card showing no service?

If your SIM card isn’t showing service, make sure the card is snugly placed in the tray, as a loose fit can interrupt the connection. Sometimes, all it takes is restarting your phone to clear up minor glitches and get things working again.

How can I check if my SIM is working?

To check if your SIM card is working, put it into a compatible phone and see if it connects to a network. If you can make calls, send texts, and browse the internet, your SIM is good to go.