Calling Vietnam from the US takes about two seconds once you know one thing, and it fails silently until you do. Vietnam's country code is +84. The part that catches almost everyone is what comes next: Vietnamese numbers are written at home with a leading zero, and that zero has to come off when you dial from another country. Leave it on and you get dead air, no error message, no clue what went wrong. This guide covers dialing into Vietnam, dialing out to home, why a number from an older page may not work any more, and the cheaper answer most travelers land on, which is not phoning at all.
Vietnam's Country Code: The Zero You Have to Drop
Vietnam holds country code 84, and the Ministry of Information and Communications files the country's numbering plan with the International Telecommunication Union, which publishes it. Every Vietnamese number you dial from outside the country starts +84. The second fact decides whether the call connects: inside Vietnam, numbers are written with a leading 0, which telecoms people call the trunk prefix. It is a domestic routing instruction, not part of the number, and the country code replaces it.
Work it through on a real number. Our support line is written in Vietnam as 0832 320 320. Strip the zero and you have the national number, 832 320 320. Put the country code in front and you get +84 832 320 320, which is what you dial from Atlanta, London or Sydney. Digit count is a useful check: Vietnamese mobile numbers are ten digits at home and nine once the zero comes off.
⚠️ The leading zero is the single most common reason a call to Vietnam fails. Dialing 011 84 0832 320 320 does not reach a wrong number, it reaches nothing, and most networks will not tell you why. If a Vietnamese number starts with 0 and you are outside the country, delete that character before you press call. If it already starts +84, it has been done for you.
Dialing In: Exit Codes and Worked Numbers
Before the country code comes your own country's exit code, the digits telling your network the call is leaving. The US Federal Communications Commission sets out the American version plainly in its international calling tip sheet: dial 011, then the country code, then the area or city code, then the number. Canada shares that 011, the UK and almost all of Europe use 00, and Australia is the outlier at 0011.
| Where You Are Calling From | Exit Code | What You Dial in Full |
|---|---|---|
| United States and Canada | 011 | 011 84 832 320 320 |
| United Kingdom, Ireland, most of Europe | 00 | 00 84 832 320 320 |
| Australia | 0011 | 0011 84 832 320 320 |
| Any mobile, any country | + | +84 832 320 320 |
That last row is the one to adopt. The + symbol is a standardized instruction meaning "insert whatever exit code applies where I am standing," and every mobile handset understands it. Hold the 0 key until a + appears, and one saved contact then works from Georgia, from a transit lounge in Doha and from a cafe in Hanoi without a single edit.
Reading a Vietnamese Number, and the Renumbering That Broke Old Ones
Vietnamese numbers come in two shapes. A mobile is a three digit network code plus seven digits, written domestically as 0 followed by nine, and it begins 03, 05, 07, 08 or 09. A landline is the zero, then a two or three digit area code, then seven or eight digits. The four codes worth knowing are Hanoi 24, Ho Chi Minh City 28, Da Nang 236 and Hai Phong 225, written at home as 024, 028, 0236 and 0225, so a Hanoi landline dialed from the US runs 011 84 24 then the eight digit local number.
Those codes are all recent, which is the part nobody warns you about and which explains a surprising share of the "it just rings out" complaints. Between February and June 2017 the Ministry changed the area codes of 59 provinces and cities. Da Nang moved from 511 to 236, Hai Phong from 31 to 225, and on June 17 the big two went: Hanoi from 4 to 24, Ho Chi Minh City from 8 to 28. Each ran alongside its old code for about a month, then the old one stopped working, all of it logged change by change in the numbering plan filings Vietnam lodges with the ITU.
The second wave was much larger. From September 15, 2018, every 11 digit mobile number became a 10 digit number, affecting close to 60 million subscribers according to Vietnam News Agency. Viettel's 0162 through 0169 became 032 through 039. MobiFone's 0120, 0121, 0122, 0126 and 0128 became 070, 079, 077, 076 and 078. VinaPhone's 0123, 0124, 0125, 0127 and 0129 became 083, 084, 085, 081 and 082. Both versions worked until November 14, 2018, and newer ranges have kept arriving since.
⚠️ Treat any Vietnamese number from a page that predates 2019 as suspect. A hotel listing or an old business card may carry a number that has not existed for years, and the failure looks identical to a dialing mistake. The tell is length: an 11 digit domestic number starting 01 is dead. If a mobile you have starts 0120, 0123, or anything from 0162 to 0169, it needs the new prefix first.
Calling Out of Vietnam: The 00 Prefix and Three Examples
Going the other way is simpler, because Vietnam uses the common exit code. From a Vietnamese line you dial 00, then the destination country code, then that country's national number with its own trunk zero removed. The rule is symmetrical: whatever leading 0 a country writes at home comes off when the call arrives from outside.
Three examples cover most readers. For an Atlanta number such as (404) 555 0123, dial 00 1 404 555 0123, since North American numbers carry no trunk zero. For a London number written 020 7946 0958, dial 00 44 20 7946 0958. For a Sydney number written 02 5550 1234, dial 00 61 2 5550 1234. On a mobile, swap the 00 for a +.
Now the honest part. International direct dial from a Vietnamese prepaid SIM is metered by the minute, and almost nobody does it. The tourist packages sold at the airport are built around data, and where they bundle voice, those are Vietnamese minutes rather than calls home. Keep 00 for emergencies.
Data Beats Dialing: How People Actually Reach Each Other Here
Vietnam skipped much of the landline era and went straight to smartphones, so almost no communication here rides a metered voice circuit. The question stops being what a minute costs and becomes whether you have a connection.
The app you will actually encounter is Zalo. It is the Vietnamese messaging platform, it is what hotels, drivers, guides and small restaurants use to confirm bookings and send directions, and there is a fair chance someone asks for your Zalo rather than your phone number within a day of landing. It handles voice and video as well as text, and installing it before you fly saves an awkward moment later. For people back home, the usual global messengers and your handset's own video calling work fine over Vietnamese mobile data.
Wi-Fi is the quiet reason a data plan matters less here than you would expect. It is close to universal in Vietnamese cafes, hotels and guesthouses, usually fast, with the password on the receipt or the wall. On unhurried city days you can run on Wi-Fi alone. It is the moving days, standing on a corner trying to reach a driver, when a local plan earns its keep, and our guide to getting around Vietnam covers why those are the days that go wrong.
Getting Connected: SIM Cards, eSIMs, and the Passport Rule
A local SIM is cheap enough that it is barely a decision. Thirty days of nationwide data runs 135,000 to 150,000 dong, roughly $5.20 to $5.75, for 5 to 7GB a day. The best value at that length is Viettel's 5G150T, VinaPhone's 5G150 or MobiFone's TK135. Viettel's plan prices exclude the cost of the SIM itself, which the carrier does not publish, so budget slightly above the headline.
| Carrier and Plan | Days | Price | What You Get |
|---|---|---|---|
| MobiFone TK135 | 30 | 135,000 dong (about $5.17) | 7GB a day, nationwide |
| Viettel 5G150T | 30 | 150,000 dong (about $5.75) | 5GB a day, nationwide |
| VinaPhone 5G150 | 30 | 150,000 dong (about $5.75) | 7GB a day, nationwide |
| VinaPhone 5G70 | 7 | 70,000 dong (about $2.68) | 8GB a day |
| Viettel 5G60T | 7 | 60,000 dong (about $2.30) | 5GB a day |
| MobiFone tourist eSIM | 1 | Free | 10GB in 24 hours, one per passport |
Registration is where visitors get caught out. Under Decree 49/2017, a subscription can only be registered against an identity document presented in the original, and for a foreign national that means your physical passport. Photocopies and phone photos are refused, every time, by every carrier. Viettel's counter process includes a live photograph of the passport and a live selfie, with no file uploads. An eSIM additionally needs an unlocked, eSIM capable handset. You can pre-register with Viettel's tourist service before you fly, and MobiFone's equivalent asks for your passport number and your e-visa application number, then activation by calling 900 once you land.
Kiosks operate in the international arrival halls at Noi Bai Terminal 2, Tan Son Nhat, Da Nang, Cam Ranh and Phu Quoc, typically staffed for every arriving flight including the late ones. MobiFone grants arriving visitors a free tourist eSIM carrying 10GB for 24 hours, one per passport, a sensible bridge if you land at 1am. Counters take cash dong, cards and VietQR. VinaPhone packages auto renew, so text HUY followed by the plan name to 888 before you leave.
⚠️ Check the package is nationwide before you pay, because some are province locked. MobiFone's 125,000 and 150,000 dong tiers are sold on enormous headline allowances, and a "1000GB a month" figure collapses to about 31GB a month, or 2 to 4GB a day, the moment you leave the province where the SIM was registered. For anyone moving between Hanoi, Hue, Hoi An and the south, that is the wrong package bought for the right reason. TK135, the FR tourist packs, 5G150T and 5G150 are all nationwide.
One tax point explains why mobile data has not got cheaper lately. Vietnam cut value added tax from 10% to 8% on most goods and services under Resolution 204/2025/QH15, which runs to the end of 2026, but telecommunications is excluded and stays at 10%. Roaming on your home carrier remains the zero effort option and is defensible for a two day stopover, but beyond that a single roaming day usually costs more than a whole month bought locally. Our Vietnam packing list covers the handset side.
Seven Hours Ahead, All Year: When to Place the Call
Vietnam sits at UTC+7 and does not observe daylight saving, which is what makes the arithmetic slippery. The country never moves, so every difference you memorize gets broken twice a year by the other end moving instead. Hanoi is 12 hours ahead of the US East Coast in the American winter and 11 in summer, 15 then 14 ahead of the West Coast, 7 then 6 ahead of the UK, and 3 to 4 hours behind eastern Australia. Our guide to time in Vietnam has the full picture.
The reliable windows sit at the edges of your day. From the US East Coast, 8am to 10am reaches a Vietnamese evening and 9pm reaches breakfast there the next morning. From the UK, a 9am to noon call lands in the Vietnamese mid to late afternoon, the easiest overlap the two countries have. Calling out runs the same logic in reverse. If you need us rather than home, our support line runs 08:00 to 21:00 Vietnam time, seven days, with the number on our contact page.
A Few Parting Notes on Staying Reachable
Three things carry most of the value here. Save every Vietnamese number in +84 format with the leading zero removed. Treat any number from a page older than 2019 as unverified until it rings. And buy a nationwide package rather than a province locked one, then stop thinking about phone calls altogether, because the country runs on data and expects you to as well.
The paperwork and the phone intersect in one place. Registering a SIM requires your original passport, and MobiFone's pre-registration asks for your e-visa application number, so the visa has to exist before the SIM does. Beyond that, Vietnam is easy to stay connected in: coverage is good, data is cheap, Wi-Fi is everywhere, and the only fiddly part is one digit at the front of the number. If you are still weighing the trip itself, our notes on whether Vietnam is safe for travelers are a fair place to start.