Train from Porto to Lisbon

As in many European countries, Portugal's high speed trains are cheaper if booked in advance - but the savings aren't nearly as much as in say France or Italy, where the fast trains become super expensive at the last minute. So there isn't as steep of a penalty for not booking in advance. When I was in Portugal, I didn't have a firm agenda, so I didn't book any trains in advance. I actually didn't take many fast trains - sometimes the regional trains worked better. (Fast trains are best between Porto and Lisbon.)

If you are the kind of traveler who can make firm plans in advance and stick to them, just book your train ticket as soon as you can. Pay attention to the station you want in Lisbon - there are several. In Porto, you'll have to take a short ride from São Bento station most likely to Campanha station where the fast trains leave from.

I just took the train from Lisbon to Porto 10 days ago and bought my ticket at the last minute—less than 45 minutes prior to departure, but only because I wasn’t certain when I would arrive. (Good thing, because I landed 6 hours later than anticipated.) But …. If you can book ahead of time, go for it. My ticket was only about €15 more than if I had booked in advance, so it wasn’t prohibitively expensive. All that was left, though, were spots in first class, which is what I had planned to take anyway. On the trip back to Lisbon from Porto I booked 24 hours in advance and didn’t have any trouble getting a seat on a Saturday afternoon.