Before you start

Your original passport — registration is mandatory and tied to it
A Hanoi address or hotel details
An unlocked handset, or an eSIM-capable one for in-store eKYC
For fibre, a lease and usually the landlord's consent

Step-by-step

1
Bridge the first days with a travel eSIM
A data eSIM bought before landing covers the gap while you find an address and a store, and removes the pressure to accept whatever a kerbside vendor is selling at Nội Bài arrivals. It is not a substitute for a registered line, because bank onboarding will not accept it.
Mobile appWho: YouDay 1
2
Buy at a branded Viettel, VinaPhone or MobiFone store
Staff scan your passport and register the line to you. Viettel has the widest national coverage and is the safe default if you will travel to the mountains; VinaPhone and MobiFone are equally good inside Hanoi. Airport counters are official and fine; the stalls outside are not.
In personWho: You15–30 minutesFrom about VND 150,000 for SIM plus first package
3
Confirm on the spot that the line is under your name
If nobody asked for your passport, the number is registered to someone else. Vietnam has blocked millions of improperly registered SIMs in successive enforcement sweeps, and those are precisely the pre-activated ones. Ask the assistant to show you the registration record before you leave the counter.
In personWho: You
4
Add a monthly data package through the carrier app
Data in Vietnam is genuinely cheap — a generous monthly package costs the equivalent of a few dollars. There is little point rationing it. Top up through the carrier app, a bank transfer or a scratch card from any convenience store.
Mobile appWho: YouMinutes≈US$5–10 per month
5
Ask what fibre the building actually has before you sign a lease
Hanoi fibre is fast and costs VND 200,000–400,000 a month, but many alley houses and older collective blocks run one shared line split across several tenants, and the advertised speed is the building's, not yours. If you work remotely, ask for a speed test in the actual flat, on the actual line, before you commit.
In personWho: You
6
Plan for the outages that come with the summer storms
Northern Vietnam gets typhoon remnants and violent summer thunderstorms, and Hanoi's overhead cabling takes the consequences. Power and fibre cuts of a few hours are ordinary in July and August. A phone with a good tethering allowance and a laptop that holds charge is the whole mitigation, but it is worth having deliberately.
Mobile appWho: You

Documents you’ll need

Original passport for the SIM registration
Hanoi address or hotel details
Lease and landlord consent for a fibre installation
A Vietnamese bank account or cash for the monthly fibre bill

Things most newcomers don’t know

A SIM not registered to your passport is a SIM that can be switched off without notice.

Decree 49/2017 and the Telecom Law require carriers to verify a foreigner's passport when issuing a line, and regulators have found millions of numbers registered against false or duplicated identity details and had the carriers block them. Pre-activated SIMs sold ready-to-use are exactly the population targeted. Beyond the risk of losing the number, a line registered to a stranger cannot be used to receive bank one-time passwords, which quietly blocks your whole banking setup.

Source: Decree 49/2017 / Telecom Law

The SIM is a prerequisite for the bank, which is a prerequisite for almost everything else.

Vietnamese banks send OTPs to a local number and increasingly tie app onboarding to it, so the order is address, then ward police declaration, then SIM, then bank, then any contract that needs a Vietnamese payment method. Newcomers try to do these in parallel and lose a week discovering the dependency chain one refusal at a time.

Source: provider consensus

In an alley house, 'fibre included' can mean one line split six ways.

Hanoi's ngõ and ngách addresses are frequently subdivided houses where the owner runs a single connection and shares it across tenants, or older collective blocks where the last hundred metres is not fibre at all. The advertised plan speed is the building's. If your income depends on video calls, insist on a speed test in the room you will work in, at an evening hour, before signing.

Source: community-reported

Vietnam's international bandwidth still runs through a small number of fragile submarine cables.

The country's undersea cables have suffered repeated simultaneous faults, and when several are down at once, domestic traffic stays fast while anything hosted abroad — video calls, foreign cloud services, some VPNs — degrades badly for days or weeks. Nothing you buy locally fixes it. Remote workers should know the failure mode exists and keep a mobile fallback on a different carrier.

Source: community-reported

Common mistakes to avoid

Buying a pre-activated SIM from a kerbside stall and finding it registered to a stranger.
Trying to open a bank account before you have a properly registered local number.
Taking a landlord's word on internet speed rather than testing it in the flat.
Assuming an alley address can get its own fibre line when the building shares one.
Letting a prepaid number go dormant while abroad and losing the number your bank sends OTPs to.

Some of this may be out of date. Spotted something inaccurate? Help us keep it right for the next newcomer.