Roaming in Vietnam: Which carrier your home telco prefers

The Vietnam carrier your home telco partners with determines the 4G/5G coverage, speed, and reliability you’ll get while roaming. Vietnam has three major mobile networks: Viettel (the largest with the best rural coverage), Vinaphone (strong in urban areas), and Mobifone (smaller, focused on cities). If your home carrier has an agreement with a weaker partner, you could face slow data and dropped calls even if you’re paying for a premium roaming plan.

Knowing which partner your provider prefers helps you decide whether roaming is sufficient or whether a local eSIM makes more sense. For instance, if your home network roams on Mobifone and you plan to visit Sapa or Ha Giang, you’ll likely experience poor signal. In that case, a local eSIM on Viettel would guarantee reliable connectivity.

Viettel has the most international roaming agreements — over 180 partners — including most major carriers from Korea, Japan, the US, and Europe. Vinaphone has strong agreements with many Asian operators (Docomo, SoftBank, China Mobile, KT) and some European carriers. Mobifone has fewer international roaming partnerships, typically limited to smaller or budget operators.

You can check the official roaming partner lists on each carrier’s website: Viettelroaming.vn, Vinaphone.com.vn, and Mobifone’s roaming page. These public resources show which foreign networks have agreements with each Vietnam carrier, helping you anticipate what your home provider might use.

Korean carriers (SKT, KT, LG U+) primarily roam on Viettel, with Vinaphone as a secondary partner. Japanese carriers: Docomo typically uses Vinaphone; SoftBank may use Viettel or Vinaphone; au (KDDI) mostly uses Viettel. US carriers: T-Mobile roams on Viettel, AT&T uses Vinaphone, and Verizon uses both with Viettel preferred. European operators such as Orange, Vodafone, and Deutsche Telekom default to Viettel due to its wider coverage.

Russian carriers (MTS, Beeline, Megafon) all primarily roam on Viettel. Chinese carriers (China Mobile, China Unicom, China Telecom) use both Viettel and Vinaphone, with the actual partner varying by SIM type and region. The pattern is clear: Viettel is the most commonly preferred partner for international roaming in Vietnam.

The easiest way is to visit your home carrier’s roaming webpage and search for ‘roaming Vietnam partner’. On iPhone, go to Settings > Cellular > Network Selection: if Viettel appears first when you disable automatic selection, your carrier prefers it. On Android, navigate to Settings > Connections > Mobile Networks > Network Operators and try the same manual search.

You can also call your carrier’s roaming hotline or check the app — some allow manual network selection for emergencies. If your carrier partners with Mobifone, consider buying a local Viettel or Vinaphone eSIM for guaranteed coverage during your trip.

Roaming costs can be high — typically $10–20 per day — and often come with capped 4G speeds that depend on the partner network. If your home carrier uses Mobifone and you’re traveling to areas like Sapa, Ha Giang, or Phong Nha, a Viettel eSIM will give you reliable signal where Mobifone struggles. For city stays, Vinaphone is also a solid choice.

A local eSIM costs roughly $2–3 per day for 5GB or more high-speed data on the same networks, with native speed and no throttling. Most modern smartphones support dual SIM: keep your home SIM for calls and SMS, add a local eSIM for data. This setup works on all recent iPhones and Android devices.

Roaming is convenient — no installation required — but it’s pricey and partner-dependent. A local eSIM is cheaper, gives you a full choice of network (Viettel or Vinaphone), and is easy to install via QR code before you arrive. For trips over 3 days or when traveling outside major cities, a local eSIM often provides better value and more reliable coverage.

We sell Viettel and Vinaphone eSIMs covering 7 to 30 days with 5GB of high-speed data per day — see our plans below at simvietnam.telebox.vn.