A Note on the Name for San Sebastian
San Sebastian is called Donostia in Basque. You will often see San Sebastian-Donostia and sometimes just Donostia written (especially on buses).
San Sebastian de los Reyes, on the other hand, is a suburb of Madrid. You don't want this one!
What's the Best Way to Get from Barcelona to San Sebastian?
Now that Vueling flies from Barcelona to San Sebastian, flying and train probably share the honors for the easiest way to get between these two cities. On the one hand, you have the shorter flight (one hour versus at least five and a half on the train), on the other hand you have the simple job of jumping on a train and settling into your journey rather than having to face the hassle (and cost) of airport transfers and check-in times.
Bilbao or San Sebastian First?
Most visitors to the Basque Country visit both San Sebastian and Bilbao. If you're deciding where to stop first, bear in mind that transport to San Sebastian is quicker and cheaper than to Bilbao. You can visit Bilbao as a day trip from San Sebastian.
Stops en Route From Barcelona to San Sebastian
If you're heading to San Sebastian for the tapas, you should consider stopping in Logroño on the way. The city is a new favorite for tapas in Spain.
Barcelona to San Sebastian by Train and Bus
The train from San Sebastian to Barcelona takes about 5h30 and costs about 40 to 50 euros. There are two or three trains per day. Trains from Barcelona to San Sebastian depart from Barcelona Sants station.
Buses from Barcelona to San Sebastian cost about 40 euros and takes about eight hours, with departures throughout the day.
Barcelona to San Sebastian by Car
The 550km drive from Barcelona to San Sebastian takes about five hours and thirty minutes, traveling mainly on the AP-7, AP-2, AP-68 and AP-15 roads. Note - AP roads are toll roads.
Flights From Barcelona to San Sebastian
Vueling flies from Barcelona to San Sebastian. Flights cost from 70 euros (often a lot more). There are two or three flights a day (the first is very early in the morning). You can compare prices on flights to Spain.