Another way of doing this by rail with a bit of a detour is to go via Vigo and Porto - you'd take trains from Barcelona to Vigo (via Madrid), the Celta from Vigo to Porto, and then a train onwards to Lisbon from there. There are two stations in Vigo and it's likely you'd arrive at one and depart from the other.

Looking at times for 17th November (a random weekday around a month in the future), there are two direct trains from Vigo to Porto, one early morning and one in the evening, meaning you'd need to break your journey somewhere along the way.

An alternative to this could be to take the 0740 from Barcelona to arrive in Vigo at 1538, make your own way to Valença, and then you have a choice of trains to Lisbon with the last one being at 2024 - giving you around six hours to get from Vigo to Valença (Portugal is one hour behind Spain). Vigo to Valença is 33km via the AP-9 motorway.

Frustratingly, there's a bus which leaves Vigo at 1945 arriving at Ponte Internacional (in Tui) at 2106, but then you'd need to make your own way to Valença station on foot and it's likely you'd just miss the last departure to Lisbon by around five minutes. The nearest rail station would be Guillarei, but the last train from Vigo leaves at 1410. Likewise, the last train to Lisbon leaves Porto around half an hour before the train from Vigo arrives.

Unfortunately the sleeper train from Barcelona to Vigo no longer runs.

Another way of doing this by rail with a bit of a detour is to go via Vigo and Porto - you'd take trains from Barcelona to Vigo (via Madrid), the Celta from Vigo to Porto, and then a train onwards to Lisbon from there. There are two stations in Vigo and it's likely you'd arrive at one and depart from the other.

Looking at times for 17th November (a random weekday around a month in the future), there are two direct trains from Vigo to Porto, one early morning and one in the evening, meaning you'd need to break your journey somewhere along the way.

An alternative to this could be to take the 0740 from Barcelona to arrive in Vigo (Urzáiz) at 1538, make your own way to Valença, and then you have a choice of trains to Lisbon with the last one being at 2024 - giving you around six hours to get from Vigo to Valença (Portugal is one hour behind Spain). Vigo to Valença is 33km via the AP-9 motorway.

To get from Vigo to Tui, you can check bus times on bus.gal. There appears to be a bus leaving Vigo E.I. (Estación Intermodal, next to Vigo Urzáiz station) at 1630, arriving at Tui (Praza de Galicia) at 1726, giving you ample time to cross the bridge (Google Maps says Tui Praza de Galicia to Valença station is a 46 minute walk). This should allow you to connect into the 1810 (again, remember Portugal is an hour behind Spain, so this isn't quite as tight as it sounds) departure from Valença to Lisbon, changing at Nine and arriving at Lisboa Oriente at 2322.

Unfortunately the sleeper train from Barcelona to Vigo no longer runs.