We are considering renting a car for three weeks in Spain but plan to travel to Portugal as well. Do car rental companies allow you to cross the border into Portugal from Spain and back again?
Yes.
You can check the rental company terms and conditions, but there should be no issues going between Spain and Portugal. We’ve never had an issue. If you were traveling to some Eastern European countries there might be some restrictions.
There are no issues crossing the border but there are huge fees for returning a car to another country. You can visit most of the countries in Europe in a rental car without any problems excluding using ferries.
I have hired a car several times in Portugal and taken it into Spain. Presumably it’s similar in reverse.
I have had three scenarios - one company didn’t charge a premium; the second charged us an extra fee for each day that the car was in Spain; and the third charged us a premium for the entire hire, even though we were only in Spain for a week.
You need to check the hire terms to ensure that you don’t invalidate the insurance by taking it into Portugal.