Vietnam has cheap, fast and widely available mobile data, and getting connected is one of the easier parts of arriving. The choice is between a physical local SIM, a local eSIM, and an international roaming eSIM, and the right answer depends on your phone and on how much you care about the first hour.
The short answer
If your phone takes a physical SIM and is unlocked, buy a local tourist SIM at the airport on arrival. A local SIM is far cheaper than roaming from home and cheaper than most travel eSIMs, and the data allowances are generous. The airport counter is the convenient place to buy one rather than the cheapest.
If your phone is eSIM-only, or you want to be connected before you reach the arrivals hall, buy a local eSIM online before you fly. It costs more than the counter SIM and less than roaming.
If you are in Vietnam for two or three days and value doing nothing, your home carrier's roaming package is the expensive but frictionless option.
The networks
Three main operators: Viettel, Vinaphone and Mobifone. Viettel has the broadest coverage, including in the mountains and on the islands, which matters if you are going to Ha Giang, Sapa or Con Dao. In the cities all three are fine.
Coverage in Vietnam is good and the data is fast by international standards. Dead spots exist in the far north and on the smaller islands.
Buying a physical SIM
Counters in the arrivals halls at Hanoi, Da Nang and Ho Chi Minh City sell tourist SIMs with a data allowance over a fixed number of days, and they will install and activate it for you. Bring your passport — registration is required and the staff handle it.
Buying in town from an official operator store is cheaper than the airport and takes longer. Buying from a street kiosk or a convenience store is cheapest and the registration is sometimes handled less carefully, which is worth avoiding.
What to check at the counter
How many days the package runs and what happens at the end. Whether the data is genuinely unlimited or throttled after a threshold. Whether it includes calls, which you probably need for Grab drivers and hotels. And that the SIM is registered in your name with your passport, which is a legal requirement.
eSIM
All three Vietnamese operators sell eSIMs, and so do a number of international travel-eSIM companies. The practical difference is that a local eSIM uses a Vietnamese network directly, while many travel eSIMs roam onto one.
Buy before you fly, install on arrival at the first wifi you reach, or install before leaving home and activate on landing. The advantage is being connected the moment you clear immigration, which is worth something if you are getting a Grab immediately.
The usual reason people choose an eSIM is to keep the home number active alongside it for messages and two-factor codes — though whether that works depends on your handset, your carrier and how the lines are configured, and a dual-SIM phone with a physical local SIM can do the same thing.
Dual SIM and keeping your number
If your phone has a physical slot and eSIM support, the neat arrangement is your home number on one and a Vietnamese data plan on the other, with data set to the Vietnamese line and your home line on calls and texts only. Turn off data roaming on the home line explicitly, or background traffic may be billed at your carrier's roaming rates.
Roaming from home
Most American carriers sell an international day pass or a travel bundle. It is the most expensive option per day by a long way, and the allowances are usually much smaller than a local SIM's.
For a short stop it is defensible. For two weeks it is not.
What you will actually use it for
Grab, constantly, which is the single biggest reason to be connected here. Maps. Translation. And messaging apps — Zalo is the Vietnamese standard and many hotels, drivers and tour operators will want to reach you on it rather than by email.
Wifi
Nearly universal in hotels, cafes and restaurants, and generally fast and free. That is not a substitute for mobile data when you are standing on a street trying to get a car, but it does mean you need less data than you think.
If something goes wrong
Operator stores are easy to find in any sizeable town and are the place to take a SIM that is not working. Keep the receipt and the packaging, which carries the number. If an eSIM fails to activate, the seller's support is the only route and that is a reason to buy from an established one rather than the cheapest listing.
What to do, concretely
Unlocked physical-SIM phone, trip of a week or more: buy at the airport counter, keep your home SIM in the tray if you have dual slots. eSIM-only phone: buy a Vietnamese eSIM online before you fly. Either way, keep your home number reachable for two-factor codes, which is the thing people forget until a bank wants to text them.
FAQ
Should you buy a SIM or an eSIM in Vietnam?
If your phone takes a physical SIM and is unlocked, buy a local tourist SIM at the airport on arrival. A local SIM is far cheaper than roaming from home and cheaper than most travel eSIMs, and the data allowances are generous. The airport counter is the convenient place to buy one rather than the cheapest.
Which Vietnamese network has the best coverage?
Three main operators: Viettel, Vinaphone and Mobifone. Viettel has the broadest coverage, including in the mountains and on the islands, which matters if you are going to Ha Giang, Sapa or Con Dao. In the cities all three are fine.
Where do you buy a tourist SIM in Vietnam?
Counters in the arrivals halls at Hanoi, Da Nang and Ho Chi Minh City sell tourist SIMs with a data allowance over a fixed number of days, and they will install and activate it for you. Bring your passport — registration is required and the staff handle it.
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