The Principality of Andorra is located in a valley in the mid-Pyrenees and consequently has neither an airport nor a railway. The only way to enter and leave Andorra is by automotive transport. One may enter Andorra via either the border with Spain or France.

How can you get to Andorra without buying a tour package?

Airport Andorra. The nearest international airports are located in Barcelona (Prat) and in Toulouse (Blagnac), each about 200 km away from Andorra. It takes approximately 3 hours to get to Andorra from either the Barcelona or Toulouse airport by bus.

Look here for details: all-andorra.com/airport-to-get-to-andorra/