Before you start

Passport plus valid visa (visitors), or a physical Iqama (residents)
An unlocked, GSM-compatible handset
Your physical presence, for the biometric capture
For postpaid: an active Iqama and usually a Saudi account or card

Step-by-step

1
Buy a prepaid line at an official store on arrival
STC, Mobily and Zain all have stores across Khobar, and King Fahd International has carrier kiosks. Start prepaid — it activates on your passport and visa in one visit. Avoid unofficial resellers entirely; a line not properly registered to you is worse than no line.
In personWho: You, with a carrier agent15–30 minutesStarter packs roughly SAR 30–50
2
Complete the biometric registration
The agent scans your ID and captures a fingerprint verified against the national identity system before the line joins the network. Mandatory for residents and visitors and impossible to do remotely, which is why an all-online arrival plan does not work in Saudi Arabia.
In personWho: YouSame visitIncluded
3
Lock the network manually before you do anything else
Set your handset to manual network selection on your Saudi carrier, and turn off data roaming. Along the Khobar coast and the causeway approach the Bahraini networks are within reach, and a phone left on automatic will register on one and start billing international roaming from inside Saudi Arabia.
Mobile appWho: YouDay oneFree, and it prevents a real bill
4
Migrate the line to your Iqama the week it is issued
A line opened on your passport must move onto the Iqama. Residents can usually do this in the carrier app through Nafath rather than returning to a store. Skipping it is what breaks Nafath and banking logins later, with no error message naming the phone.
Mobile appWho: YouSame week as Iqama issuanceFree
5
Add a Bahrain plan or a travel eSIM if you cross often
Saudi carriers sell roaming bundles for Bahrain, and a cheap Bahraini prepaid line or travel eSIM is an alternative for regular crossers. Deciding this in advance is far cheaper than discovering standard roaming rates after a weekend of maps and messaging.
Mobile appWho: YouBefore your first crossingVaries; bundles are far cheaper than default roaming
6
Audit your lines on Mutasil
CST's Mutasil service lists every number registered to your ID, free of charge. Use it to confirm nothing was opened in your name without consent and to check your position against the per-ID cap before trying to add a line for a family member or a work device.
OnlineWho: YouInstantFree

Documents you’ll need

Passport plus valid visa (visitors) or physical Iqama (residents)
Live fingerprint captured at the point of sale
Border entry number for visitor registration
Saudi account or card for postpaid direct debit

Things most newcomers don’t know

You can be billed for Bahraini roaming without ever leaving Saudi Arabia.

The causeway is 25 kilometres of water and Bahraini network coverage carries across it. Handsets left on automatic network selection along the Khobar coastline and near the causeway approach will intermittently register on a Bahraini operator and start charging international roaming. The charge appears weeks later with no obvious cause, and people blame the carrier. Manual network selection with roaming disabled removes the problem entirely and takes thirty seconds.

Source: Community-reported across Eastern Province residents; carrier roaming behaviour

The SIM is the root of your digital identity, and mis-registration poisons everything downstream.

Nafath sends its approval push to the number registered against your Iqama. A line still on your passport, or in an employer's name, causes silent authentication failures across banking, Absher, Qiwa and Muqeem, with no message pointing at the phone as the cause. People spend days debugging a bank app. Migrate the line in the same week the Iqama is issued and the class of problem disappears.

Source: CST SIM registration rules; MoI Nafath

None of this can be done remotely, so plan your first hours with data already working.

The live fingerprint capture means a store or staffed kiosk visit is unavoidable, and visitor eSIM activation inside an app is frequently blocked by a Saudi-ID check. King Fahd International is a long drive from the cities, so arrive with roaming enabled or a travel eSIM loaded — you will want a ride-hailing app functioning before you clear customs, not after.

Source: CST; carrier point-of-sale practice

The per-ID line cap catches returning contractors hardest.

Residents may hold only a small number of lines per Iqama, prepaid and postpaid both counting. This region has a lot of people on second and third rotations, and a dormant line from a previous contract — or one an old employer opened in your name — consumes the allowance and gets a new purchase refused at the counter with no explanation. Check Mutasil first and release what you no longer need.

Source: CST Mutasil

Common mistakes to avoid

Leaving automatic network selection on and paying Bahraini roaming from inside Saudi Arabia.
Keeping the line registered to your passport after the Iqama is issued.
Using an employer's or colleague's number, so you do not control the identity your logins depend on.
Crossing to Bahrain on default roaming rates instead of a bundle or a local eSIM.
Hitting the per-ID cap because of a dormant line from an earlier contract.

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