Do US SIM Cards Work in Canada and Mexico? A Traveler's Roaming Guide

2026-11-10

The short answer: yes, but not every plan includes data. Higher-tier postpaid plans usually cover Canada and Mexico roaming outright; prepaid is where travelers get caught — some prepaid plans have no data roaming at all, so you can call and text across the border but need a paid add-on to get online. Check your plan tier before you travel.

1. T-Mobile: postpaid includes data, prepaid needs an add-on

• Postpaid: Experience Beyond includes 30GB of high-speed data in Canada and Mexico, Experience More includes 15GB, and both keep working at reduced speeds after that. Essentials includes unlimited calls and texts, but data runs at up to 128 Kbps — enough for messages, not for video.
• Prepaid: no data roaming by default. Add the $5-a-month Mexico and Canada bundle before you leave — it covers unlimited calls and texts between the US, Mexico, and Canada plus up to 5GB of high-speed data. The Unlimited Plus Monthly plan includes calls and texts between the three countries.
• Watch out: roaming is built for short trips. If most of your usage stays on a foreign network for months, the carrier can restrict or end the service.

2. AT&T: unlimited plans include both countries; prepaid depends on the tier

• Postpaid unlimited plans: all include unlimited talk, text, and data in and between the US, Canada, and Mexico, with nothing extra to set up. Some premium plans add 20 Latin American countries.
• Prepaid: Unlimited Enhanced Plus and Unlimited Ultra include Mexico and Canada, with a 25GB monthly cap on data in Canada. Other prepaid tiers have no data roaming in Canada or Mexico.
• Plans without coverage: postpaid lines can use the International Day Pass, billed per day (confirm the current price at purchase time); prepaid lines can buy a 7-day travel add-on with 5GB of data. Check whether your plan is on the included list before you cross the border.

3. Lycamobile: Canada is covered, Mexico is not the same deal

• Unlimited Plus and Unlimited Pro include Canada roaming: 5GB of roaming data plus calls and texts to Canada, with no need for a Canadian SIM.
• The key condition: the plan must be activated in the US first. Once in Canada, turn on data roaming and it works; the 5GB allowance runs on the plan's 30-day validity.
• Mexico is not part of Lycamobile's Canada roaming benefit, so confirm coverage for Mexico separately instead of assuming both neighbors work the same way.

4. Four things to do before you cross the border

• Check your tier: confirm in the carrier's app or on its site whether your plan includes Canada and Mexico — don't guess from the word "unlimited."
• Turn on roaming: enable data roaming in your phone's settings so it connects to a local carrier automatically once you're across.
• Set it up before you leave: buy any bundle or add-on while you still have service in the US. Adding one with no connection abroad is painful.
• Keep a backup: if your plan has no roaming, pair a local travel eSIM for data with your US SIM kept on for verification codes — the dual-SIM setup is the safest combo.