There are two public transport options for travelling between Porto and Santiago da Compostela.
There is a twice daily "Celta" train connecting Porto Campanha Station and Vigo in Galicia. Only the morning train has an onward connection to Santiago da Compostela according to , the Spanish Railways website.
Daily Schedule as follows:
Name: TRENCELTA No. 12424 MD
Dept: Porto Campanha 08.15
Arr: Vigo Guixar 11.30
Dept: Vigo Guixar 12:13
Arr: Santiago da Compostela 13:37
There is a daily bus service operated by associates) that departs Porto Casa da Musica Bus station as follows:
Dept: Porto 12:45
Arr: Santiago Compostela 17:45
Transit Time: 4h00 (Note time in Spain is one hour ahead of Portugal.)
This service operates via Porto Airport (15 minutes later), Braga and Vigo.