Child Car Seats in Spain: The Rental Rules

Spain does not leave child car seats to parental instinct, airport fatigue, or a quick "they'll be fine for ten minutes" decision.

If a child is 135 cm tall or under, they must use an approved child restraint system that fits their height and weight. As a general rule, they must also travel in the rear seats. That applies in a hire car just as much as it applies in your own car.

The good news is that the rule is simple once you translate it into rental language: tell the supplier the children are travelling, give their height and weight, and reserve the right infant seat, child seat, or booster before you arrive.

The 135 cm rule

In Spain, children who are 135 cm or shorter must use a homologated child restraint system. The Spanish traffic authority, the DGT, also recommends continuing to use a suitable restraint until a child reaches 150 cm if the adult seat belt does not fit properly.

The legal cut-off is height, not age. A tall 10-year-old may be able to use the normal belt legally, while a smaller 12-year-old may still need a booster.

The seat belt test is practical: the diagonal belt should sit across the shoulder and chest, not the neck, and the lap belt should sit low over the hips, not across the stomach. If the belt sits badly, use a booster even if the child is over 135 cm.

Children usually sit in the back

For children 135 cm or under, the rear seat is the default. Spain allows the front passenger seat only in limited cases:

• The vehicle has no rear seats.
• All rear seats are already occupied by other children using child restraints.
• It is not possible to install all the required child restraints in the rear.

If a child must travel in the front under one of those exceptions, they still need the correct child restraint. If the seat is rear-facing, the front airbag must be switched off.

Which seat should you book?

Rental companies may still describe child seats in old Group 0, 1, 2, and 3 language, but the newer European R129 standard is based mainly on the child's height. Either way, the supplier needs the same information: age, height, and weight.

As a plain guide:

• Babies and small toddlers need an infant or toddler seat with its own harness. Rear-facing is required under the R129 standard until at least 15 months and is the safer position for longer where the seat allows it.
• Younger children who have outgrown an infant seat still need a proper child seat with harness or impact protection, matched to their size.
• Older children under 135 cm usually need a high-back booster or booster seat so the adult belt sits correctly.
• Children between 135 cm and 150 cm may legally use the normal belt if it fits, but a booster is often still the safer and more comfortable answer.

If you are bringing your own seat, check that it has an orange European approval label. R129 is the current standard for new seats sold in the EU. Older R44 seats can still be used if they are approved, undamaged, and suitable for the child, but they can no longer be sold new or second-hand in the EU.

Bringing your own seat vs hiring one

Bringing your own seat gives you a seat you know and a fit you have already tested. It is often the best option for babies, nervous toddlers, or children with a seat that is adjusted very specifically.

Hiring one is easier when you want less luggage, especially for booster-age children. The trade-off is that you need to reserve it in advance and check it before you leave the pick-up point.

Before driving away, confirm:

• The seat is the type you booked.
• It is clean, intact, and has no obvious cracks or missing parts.
• It fits the car properly.
• The harness or belt path is not twisted.
• Your child is within the height and weight range shown on the label.

If something looks wrong, ask for a different seat before you set off. This is not the moment to be polite and improvise.

Tell the supplier early

Child seats are not magic objects that appear from a cupboard when everyone is already tired. They are extras with limited stock, and the correct size matters.

When booking your hire car, add the child seat request at the same time as the vehicle. Give each child's age, height, and weight. If you are landing at a busy time, or travelling in July and August, do not leave it until the desk.

With RentaCarBestPrice, you can arrange child restraints before collection so the right seat is ready with the car. That fits neatly with Alicante Airport car hire and Valencia Airport car hire, where families usually want the handover to be short, clear, and free of last-minute negotiation.

The short version

If your child is 135 cm or under, book an approved child restraint for Spain. Expect them to sit in the back, give the supplier accurate height and weight details, and check the seat before you drive away.

If your child is over 135 cm but the belt still cuts across the neck or stomach, use a booster anyway. The law sets the minimum. Your child's actual fit in the car decides what is sensible.