Is Porto day trip from Lisbon worth it?

I assume you mean total travel time to go and return? Alfa Pendular train journey takes 2.5 hours. But to answer your question, Porto definitely worth the trip, so different from Lisbon and one of my favorite places. However, I would never go as a day trip, at least stay overnight.

Unfortunately I can't do overnight because I already booked hotel in Lisbon for the entire trip. I would spend 8-9 hours in Porto. Is it still worth it?

Thanks!!!
Vera

Is this the only daytrip destination you're considering? In addition to the common daytrip to nearby Sintra, Evora makes a more reasonable option at 1.5 hours each way by direct train, and some trains to/from Coimbra are also about 1.5 hours. I would do those before deciding whether you need or have time for another, longer day trip.

No. Given a 5 hour train ride round trip (assuming no delays), and other travel logistics you would have very little time to appreciate Porto. There are closer alternatives for a day trip. Another option is to contact the hotel in Lisbon and see if you can opt out of one night, or eat the cost and book an inexpensive hotel in Porto.

I totally agree with the others. Don’t try to do Porto as a day trip. You will remember nothing of the day except being on the train. Opt for places closer to Lisbon - Sintra, Evora or possibly Coimbra. If you have less than a week, staying in Lisbon and Sintra can more than fill your time.
The weather is crummy today but it’s supposed to clear up and be sunny later in the week. Even a ferry ride across the Tejo to Calcilhas would be lovely if it’s warm.

Thanks so much for all the responses. I will just go to Sintra or Coimbra ( is that a best place to hear Fado?).

Thanks!
Vera

There is traditional Fado in Lisbon. The Fado in Coimbra is different and is sung by men.

I read that at museum of Fado is the one of the best place to hear Fado in Lisbon, is that true?
Since I'm traveling solo I didn't want to have a sit-down dinner with Fado.
Also, are there some special performances because be it's a holiday season?

Thanks!

I went through the Fado Museum in Lisbon in May. There was no live music there. There was a large room with a large wall with large pictures of various star fado performers over time. You could then listen, with provided headsets, to recorded music by each artist. The museum also included various photos, posters, musical instruments. Given that Fado exists primarily in Portugal, the museum is a unique experience, but in comparison to other types of museums, it is certainly small and limited. It does not satisfy the desire to hear live music. If you don’t want to go to a fado dinner show by yourself, I also took an evening walking tour that concluded with dinner and fado music. Hope that helps. The Centro do Fado in Coimbra generally has multiple performance each evening (maybe different with the season’s, maybe not 7 days a week) performed by men who are students or alumni of the university. A good performance in a small and quite intimate venue, but unique to Coimbra. By the way, I do believe there have been a few women in their fado association, but I don’t believe any have yet achieved the performance level.

Thanks so much, it helps a lot!