SJ, Sweden's state rail operator, runs one of the more relaxed pet policies covered anywhere in this guide. According to Swedish travel-advice sources describing SJ's own terms, a traveller can bring up to two dogs or other pets at no extra charge, provided the animal fits on the floor by the seat rather than needing a seat of its own.

If a dog is too large to sit comfortably on the floor, or you simply want more room, the usual option is to book the animal its own seat at the price of a youth (under-16) fare for that route. Travellers are generally advised to look for or request the 'Djur tillåtet' (animals allowed) option when booking, which places you in the designated pet-friendly section of the carriage — on SJ's trains, this section sits within standard second class.

Night trains follow broadly the same approach, and booking a private sleeping compartment is the usual way to travel with one or two dogs overnight. Because fares, exact seating rules and carriage layouts can change and SJ's own site doesn't publish a single detailed public pet page in English, it's worth confirming the current fare and booking process directly with SJ when you book, particularly for a dog too large for the floor option.